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Infected pancreatic necrosis (IPN) is a highly morbid complication of acute necrotising pancreatitis (ANP). Since there is evidence of early-onset immunosuppression in acute pancreatitis, immune enhancement may be a therapeutic option. This trial aimed to evaluate whether early immune-enhancing Thymosin alpha 1 (Tα1) treatment reduces the incidence of IPN in patients with predicted severe ANP.We conducted a multicentre, double-blind, randomised, placebo-controlled trial involving ANP patients with an Acute Physiology and Chronic Health Evaluation II (APACHE II) score ≥ 8 and a computed tomography (CT) severity score ≥ 5 admitted within 7 days of the advent of symptoms. Enrolled patients were assigned to receive a subcutaneous injection of Tα1 1.6 mg every 12 h for the first 7 days and 1.6 mg once a day for the subsequent 7 days or matching placebos (normal saline). The primary outcome was the development of IPN during the index admission.A total of 508 patients were randomised, of whom 254 were assigned to receive Tα1 and 254 placebo. The vast majority of the participants required admission to the intensive care unit (ICU) (479/508, 94.3%). During the index admission, 40/254(15.7%) patients in the Tα1 group developed IPN compared with 46/254 patients (18.1%) in the placebo group (difference -2.4% [95% CI - 7.4 to 5.1%]; p = 0.48). The results were similar across four predefined subgroups. There was no difference in other major complications, including new-onset organ failure (10.6% vs. 15%), bleeding (6.3% vs. 3.5%), and gastrointestinal fistula (2% vs. 2.4%).The immune-enhancing Tα1 treatment of patients with predicted severe ANP did not reduce the incidence of IPN during the index admission.

Multirotor analytical dynamic inflow models in the literature, such as pressure potential superposition inflow model or velocity potential superposition inflow model (VPSIM), have been shown to capture the fundamental inflow interference effects between the rotors. Some of the differences in inflow predictions seen between these analytic models and high-fidelity wake models are attributed to missing real flow effects such as wake distortion, contraction, decay, swirl, etc. As such, correction terms are needed in the analytically derived multirotor finite-state inflow models, because of the potential flow and rigid wake assumptions they are based on, in order to capture some of the missing real flow effects in them. This paper develops a systematic methodology for arriving at the needed correction terms in the VPSIM through comparisons of its inflow predictions with those of a viscous vortex particle model (VVPM). Also, a procedure is developed to assess the relative importance of individual real flow effects and the associated corrections needed for improving the overall fidelity of the VPSIM. The developed methodology is applied to the Harrington coaxial rotor using its geometric and aerodynamic data from the literature. It is shown that the addition of swirl coupling correction terms to the VPSIM significantly improves its correlations with the VVPM. Further, it is shown that the required corrections are reasonably insensitive to thrust sharing ratio conditions between the rotors.

Background: Finding reliable diagnostic markers for gastric cancer (GC) is important. This work uses machine learning (ML) to identify GC diagnostic genes and investigate their connection with immune cell infiltration.Methods: We downloaded eight GC-related datasets from GEO, TCGA, and GTEx. GSE13911, GSE15459, GSE19826, GSE54129, and GSE79973 were used as the training set, GSE66229 as the validation set A, and TCGA & GTEx as the validation set B. First, the training set screened differentially expressed genes (DEGs), and gene ontology (GO), kyoto encyclopedia of genes and genomes (KEGG), disease Ontology (DO), and gene set enrichment analysis (GSEA) analyses were performed. Then, the candidate diagnostic genes were screened by LASSO and SVM-RFE algorithms, and receiver operating characteristic (ROC) curves evaluated the diagnostic efficacy. Then, the infiltration characteristics of immune cells in GC samples were analyzed by CIBERSORT, and correlation analysis was performed. Finally, mutation and survival analyses were performed for diagnostic genes.Results: We found 207 up-regulated genes and 349 down-regulated genes among 556 DEGs. gene ontology analysis significantly enriched 413 functional annotations, including 310 biological processes, 23 cellular components, and 80 molecular functions. Six of these biological processes are closely related to immunity. KEGG analysis significantly enriched 11 signaling pathways. 244 diseases were closely related to Ontology analysis. Multiple entries of the gene set enrichment analysis analysis were closely related to immunity. Machine learning screened eight candidate diagnostic genes and further validated them to identify ABCA8, COL4A1, FAP, LY6E, MAMDC2, and TMEM100 as diagnostic genes. Six diagnostic genes were mutated to some extent in GC. ABCA8, COL4A1, LY6E, MAMDC2, TMEM100 had prognostic value.Conclusion: We screened six diagnostic genes for gastric cancer through bioinformatic analysis and machine learning, which are intimately related to immune cell infiltration and have a definite prognostic value.

In this study, for small unmanned aerial vehicle aeroacoustic predictions, an in-house acoustic code was extended for broadband noise using the empirical Brooks–Pope–Marcolini (BPM) method. The acoustic code was coupled with a comprehensive analysis tool (FLIGHTLAB) or Reynolds-averaged Navier–Stokes (RANS) method to predict the noise from a DJI 9443 CF rotor. The effects of two input parameters of the BPM method on the broadband noise were investigated, including the effective angle of attack and boundary layer parameters. The empirical formula for the boundary layer parameters was replaced with predictions using two-dimensional RANS, allowing arbitrary airfoils other than NACA0012. The boundary layer parameters were also predicted using three-dimensional RANS to capture a three-dimensional flow effect, which can be dominant in modern propellers operating at high rotational speeds. As a result, the three-dimensional effect on the boundary layer was confirmed to conflict with the BPM method, which was developed based on a two-dimensional chordwise flow database. Finally, mid- and high-frequency noise spectra were predicted from the three-dimensional hybrid RANS/LES simulation to be combined with the BPM results, thus improving the noise spectra predictions at midrange frequencies.

The objective of this study was to investigate the method, efficacy, and safety of endovascular treatment (EVT) of delayed splenic artery branch (SAB) hemorrhage after pancreaticoduodenectomy.From March 2019 to January 2022, all patients underwent EVT of SAB for delayed post-pancreaticoduodenectomy hemorrhage were included. Demographic, laboratory, angiographic, and clinical follow-up data were collected and analyzed.A total of eight patients were enrolled. In two patients, celiac axis angiography alone failed, but selective splenic artery (SA) angiography demonstrated the SAB bleeding; SAB erosions in four patients with recurrent bleeding were successfully detected by a second angiography; four patients underwent balloon catheter placement at the SA for temporary hemostasis and to further confirm the SAB bleeding before the subsequent EVT. Superselective embolization was performed in only one patient (12.5%; 1/8); covered stent implantation at the SA was performed in two patients (25%; 2/8); Embolization of the SA was performed in the remaining five patients (62.5%; 5/8). The technical success rate, clinical success rate, and in-hospital mortality were 100.0%, 87.5%, and 25%, respectively. No severe complications related to EVT occurred.EVT of SAB for delayed post-pancreaticoduodenectomy hemorrhage is effective and safe. An awareness of the SAB as a potential bleeding source, together with appropriate endovascular procedures including selective SA angiography, repeat angiography, balloon catheter placement at the SA, and applicable hemostasis protocol, could achieve a high success rate of managing SAB hemorrhage.

BackgroundThe study aimed to assess the safety and efficacy of conversion therapy with portal vein embolization (PVE) and transcatheter arterial chemoembolization (TACE) in patients with large unresectable hepatocellular carcinoma (HCC) and ipsilateral portal vein tumor thrombus (PVTT).MethodsThis retrospective study evaluated consecutive patients with initially large (≥5 cm) unresectable HCC with ipsilateral PVTT who underwent PVE + TACE at our center between June 2016 and September 2020 (Group A). Clinically equivalent patients from three centers who were receiving tyrosine kinase inhibitors (TKIs) + TACE (Group B) were included. The survival times were evaluated and compared between the two therapeutic groups.ResultsIn Group A (n = 33), the median tumor diameter was 14 cm (range, 5–18 cm) and 19 (57.6%) patients underwent radical resection 18–95 days after PVE. Radical liver resection was not performed because of inadequate hypertrophy (n = 11), pulmonary metastasis (n = 1), lack of consent for surgery (n = 1), and the rupture of the HCC (n = 1). There were no patients who underwent radical resection in Group B (n = 64) (P = 0.000). The mean and median overall survival (OS) were 736.5 days and 425.0 days in Group A and 424.5 days and 344.0 days in Group B, respectively. Compared with TKIs + TACE, treatment with PVE + TACE prolonged OS (P = 0.023).ConclusionsThis study shows that conversion therapy was safe and effective in patients with initially large unresectable HCC with ipsilateral PVTT treated with PVE + TACE. Moreover, PVE + TACE conferred more favorable outcomes than treatment with TKIs + TACE.

About 55% of hepatocellular carcinoma (HCC) cases in China are advanced HCC at the initial diagnosis. We aimed to evaluate the efficacy and safety of hepatic arterial infusion chemotherapy (HAIC) for HCC with portal vein tumor thrombosis (PVTT) compared to transcatheter arterial chemoembolization (TACE) after propensity score matching (PSM).A propensity score-matched cohort study was performed in patients with advanced HCC with PVTT who underwent either HAIC using oxaliplatin plus raltitrexed or TACE at three institutions between January 2016 and January 2021. Overall survival (OS), progression-free survival (PFS), objective response rate (ORR), and adverse events were compared between the groups.After PSM, 44 pairs of patients were assessed. The HAIC group had longer OS (11.2 [95% confidence interval [CI]: 9.9-12.5] vs. 9.0 [95% CI: 5.3-12.7] months; p = 0.010), better PFS (5.6 [95% CI: 3.7-7.9] vs. 2.0 [95% CI: 1.3-2.7] months; p = 0.006), and a higher ORR (Response Evaluation Criteria in Solid Tumors [version 1.1]: 56.8% vs. 18.2%; p 0.001) than the TACE group. In multivariate analysis, HAIC was identified as an independent favorable prognostic factor for survival.Compared to TACE, HAIC significantly increased the ORR of HCC with portal invasion and prolonged survival without causing a significant increase in severe adverse events.

An analytical coaxial rotor inflow model has been developed from potential flow theory using the pressure potential superposition approach. The coaxial rotor pressure potential superposition inflow model (PPSIM) is formulated in statespace form with structure similar to the Peters–He model, except that additional off-diagonal blocks are included in the apparent mass (M-matrix) and influence coefficient matrices (L-matrix). These off-diagonal blocks take into account mutual interference effects present in a coaxial rotor system by relating the rotor's inflows due to other rotor's pressure loadings. Induced inflow distributions on both upper and lower rotors are computed using PPSIM for comparison against predictions from high-fidelity models such as GT-Hybrid and the viscous vortex particle method (VVPM). Good agreement between PPSIM-induced inflow results and GT-hybrid as well as VVPM data has been shown for hover flight condition. At low advance ratio, there are differences in fore-to-aft inflow states between PPSIM and the high-fidelity models. This is because PPSIM assumed rigid, skewed cylindrical wake geometries for both upper and lower rotors during forward flight. But in GT-Hybrid and VVPM, wake structures are allowed to move freely in space and are mainly affected by rotor-induced velocities at low advance ratios. Owing to the close proximity between upper and lower rotors, mutual interference-induced velocities significantly distorted the rotors' wake geometries. The rigid rotor wake geometry assumptions in PPSIM and the distortion captured in higher fidelity models are the reasons behind differences in rotor-induced inflows. At higher advance ratios, wake distortion effects are less prominent since free-stream inflows are significantly larger than rotorinduced velocities. Hence, smaller differences between PPSIM inflow states and those extracted from GT-Hybrid as well as VVPM are observed at high advance ratios.

An analytical coaxial rotor inflow model has been developed in the literature by combining pressure fields of individual rotors. In such a pressure potential superposition inflow model (PPSIM), real flow phenomena such as viscous effects, flow swirls, and wake distortions are neglected. To capture real flow effects, inflow distribution predictions from the viscous vortex particle method (VVPM) are used to correct PPSIM influence coefficients (L-matrix). It is found that cosine–sine coupling is significant during hover and low advance ratios, especially on the lower rotor. Most correction terms are found to be insensitive to the thrust coefficient ratio between the upper and lower rotors. For ease of implementation, the curve-fitted correlation of each L-matrix correction element and wake skew function is found. Inflow states computed from PPSIM with curve-fitted L-matrix corrections are close to VVPM results, with an average difference of 6%.

Unresectable hepatocellular carcinoma (HCC) has a poor prognosis. We aimed to evaluate the efficacy and safety of hepatic arterial infusion chemotherapy (HAIC) for locally advanced HCC compared to transcatheter arterial chemoembolization (TACE).A propensity score-matched cohort study was performed in patients with locally advanced HCC with ≥ 4 tumors or portal vein tumor thrombosis (PVTT) who underwent either HAIC using oxaliplatin plus raltitrexed or TACE at three institutions between June 2015 and December 2021. Overall survival (OS), progression-free survival (PFS), objective response rates (ORR), and adverse events (AEs) were compared between the groups.After propensity score matching, 62 pairs of patients were evaluated. The HAIC group had longer OS (15.0 [95% CI: 12.1-17.9] vs. 9.0 [95% CI: 5.1-12.9] months; P = 0.034), better PFS (6.7 [95% CI: 5.1-8.3] vs. 4.0 [95% CI: 2.6-5.4] months; P = 0.020), and a higher ORR (RECIST 1.1: 54.8% vs. 11.3%; P 0.001) than the TACE group in the intention-to-treat population. Compared with the TACE group, Grade 1-2 nausea and vomiting occurred significantly more frequently in the HAIC group.Compared to TACE, HAIC significantly increased the ORR of locally advanced HCC with multiple tumors or portal invasion and prolonged survival without causing a significant increase in severe AEs.

Background: This retrospective study aimed to evaluate the technical feasibility and safety of the delayed catheter removal technique in trans-hepatic portal vein embolization (PVE) and to explore a suitable technique. Methods: This was a retrospective study. In 278 consecutive patients, the puncture tract of the trans-hepatic PVE was treated using the delayed catheter removal technique after PVE. The existence of peripheral hepatic hematoma formation was assessed using ultrasound (US). Follow-up examinations such as magnetic resonance imaging (MRI), computed tomography (CT), and/or US were performed to evaluate perihepatic hematoma formation, hemoperitoneum, and other major complications. Results: Instant hemostasis was achieved in all patients after the procedure. PVE-associated complications were observed in 9 patients (3.24%). No perihepatic hematoma or hemoperitoneum was found in any of the patients. Conclusion: With the appropriate technique, the delayed catheter removal technique can be reliably utilized as a substitute for hemostasis as it is simple and free. This technique should be further evaluated and compared with other methods. Advances in knowledge: This study is the first to investigate the safety and feasibility of the delayed catheter removal technique for embolizing the puncture tract of the trans-hepatic PVE.

Cadmium (Cd), a ubiquitous toxic heavy metal, with the intractable trait of low degradation, can induce multiple organ damage. Whereas, far less is known about its neurotoxicity and the specific mechanism in the chronic low Cd exposure. To investigate the chronic neurotoxicity of Cd

BACKGROUND&AIMSInfected pancreatic necrosis (IPN) is a highly morbid complication of acute pancreatitis (AP). Since there is evidence of immunosuppression in the early phase of AP, immune enhancement using Thymosin alpha 1 (Tα1), which stimulates both innate and adaptive immunity, may be a therapeutic strategy to prevent IPN. Our aim was to assess the efficacy of early Tα1 treatment on the development of IPN.METHODSWe conducted a multicenter, randomized, double-blind, placebo-controlled trial in patients with predicted severe acute necrotizing pancreatitis (ANP). ANP patients with an APACHE II score≥8 admitted within seven days of the advent of symptoms were considered eligible. Enrolled patients were assigned to receive a subcutaneous injection of Tα1 1.6 mg, every 12 hours for the first 7 days and 1.6 mg once a day for the subsequent 7 days or matching placebo (normal saline). The primary outcome was the development of IPN during the index admission.RESULTSFrom Mar 2017 through Dec 2020, 508 patients were randomized at 16 hospitals, of whom 254 were assigned to receive Tα1 and 254 placebo. During the index admission, 40/254 (15.7%) patients in the Tα1 group developed IPN compared with 46/254 patients (18.1%) in the placebo group (difference -2.4% [95%CI -7.4% to 5.0%]; p=0.47). The results were similar in four predefined subgroups. There was no difference in other major complications, including new-onset organ failure (10.6% vs. 15.0%; p=0.15), bleeding (6.3% vs. 3.5%; p=0.15), and gastrointestinal fistula (2.0% vs. 2.4%; p=0.75) during the index admission.CONCLUSIONSThe immune-enhancing Tα1 treatment of patients with predicted severe ANP did not reduce the incidence of IPN during the index admission.Trial registrationClinicaltrials.gov registry: NCT02473406.

Advanced glycation end products (AGEs)-induced inflammation and degradation of aggrecan in human chondrocytes play an important role in the progression and development of osteoarthritis (OA). Azilsartan, an angiotensin II receptor antagonist, has been licensed for the treatment of high blood pressure. However, the effects of Azilsartan in OA and AGEs-induced damages in chondrocytes have not been previously reported. The injured chondrocytes model was established by incubating with 5 μmol/L AGEs. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide was used to evaluate the cell viability of treated SW1353 cells. The gene expression levels of interleukin-1α (IL-1α), tumor necrosis factor-β (TNF-β), IL-6, a disintegrin-like and metallopeptidase with thrombospondin type motif-4 (ADAMTS-4), ADAMTS-5, Aggrecan, and Sox-4 were evaluated using quantitative real-time polymerase chain reaction and their protein levels were determined using enzyme-linked immunosorbent assay or Western blot analysis. Mitogen-activated protein kinase p38 pathway was surveyed using phosp-p38 level and its specific inhibitor SB203580 was employed to block the p38 pathway. The overexpression of Sox4 plasmid was transfected into SW1353 cells to assess its regulation on ADAMTS-4 and ADAMTS-5. Azilsartan reduced AGEs-induced production of proinflammatory cytokines, such as IL-1α, TNF-β, and IL-6. Azilsartan prevented AGEs-induced expressions of ADAMTS-4 and ADAMTS-5 as well as the reduction of aggrecan. Mechanistically, AGEs treatment increased the expression of Sox4 in a dose-dependent manner. AGE treatment increased the level of phosphorylated p38. However, treatment with the p38 inhibitor SB203580 inhibited AGEs-induced expression of Sox4, suggesting that AGEs-induced expression of Sox4 is mediated by p38. Furthermore, Azilsartan suppressed AGEs-induced phosphorylation of p38 and expression of Sox4. Finally, the overexpression of Sox4 abolished the inhibitory effects of Azilsartan against the expressions of ADAMTS-4 and ADAMTS-5. Azilsartan treatment prevented AGEs-induced inflammatory response and degradation of aggrecan through inhibition of Sox4.

The current treatment strategies for osteoporosis (OP) involve promoting osteogenic differentiation and inhibiting adipogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). According to a theory of traditional Chinese medicine (TCM), the kidneys contain an “essence” that regulate bone metabolism and generate marrow. Kidney disorders are therefore considered to be a major cause of OP as per the principles of TCM, which recommends kidney-tonifying treatments for OP. The Zuogui pill (ZGP) is a classic kidney-tonifying medication that effectively improves OP symptoms. Studies have shown that ZGP can promote the osteogenic differentiation of BMSCs, providing scientific evidence for the TCM theory linking kidneys with bone metabolism. In this review, we have provided an overview of recent studies that examined the underlying mechanisms of ZGP mediated regulation of BMSC osteogenic and adipogenic differentiation.

As simulation has become an integral part of the overall life-cycle support of aircraft, the need for effective Virtual Engineering (VE) tools to support these activities has increased. FLIGHTLAB is a state-of-the-art, aircraft modelling and simulation software tool, that has been designed to address this need and is widely used in rotorcraft design, analysis, test and evaluation, and full-flight simulation applications. This VE tool supports the development and analysis of both fixed and rotary wing aircraft with an extensive library of modelling components which have been successfully used and validated in numerous, real-world applications. These components provide comprehensive modelling of aerodynamic, structural, control and propulsion disciplines. Analyses include performance, dynamic response, stability and control, airloads, and structural loads. Graphical User Interfaces and an interactive scripting language provide user-friendly operation. This paper describes the capabilities and validation activities that have been undertaken to support the development of the commercial VE toolset FLIGHTLAB over the last 20 years and discusses future rotorcraft challenges that could be addressed by enhancements to current generation VE tools.

Osteoporosis, femoral head necrosis, and congenital bone defects are orthopedic disorders characterized by reduced bone generation and insufficient bone mass. Bone regenerative therapy primarily relies on the bone marrow mesenchymal stem cells (BMSCs) and their ability to differentiate osteogenically. Icariin (ICA) is the active ingredient of Herba epimedii, a common herb used in traditional Chinese medicine (TCM) formulations, and can effectively enhance BMSC proliferation and osteogenesis. However, the underlying mechanism of ICA action in BMSCs is not completely clear. In this review, we provide an overview of the studies on the role and mechanism of action of ICA in BMSCs, to provide greater insights into its potential clinical use in bone regeneration.

IntroductionInfected pancreatic necrosis (IPN) and its related septic complications are the major causes of death in patients with acute necrotising pancreatitis (ANP). Therefore, the prevention of IPN is of great clinical value, and immunomodulatory therapy with thymosin alpha 1 may be beneficial. This study was designed to test the hypothesis that the administration of thymosin alpha 1 during the acute phase of ANP will result in a reduced incidence of IPN.Methods and analysisThis is a randomised, multicentre, double-blind, placebo-controlled study. 520 eligible patients with ANP will be randomised in a 1:1 ratio to receive either the thymosin alpha 1 or the placebo using the same mode of administration. The primary endpoint is the incidence of IPN during the index admission. Most of the secondary endpoints will be registered within the index admission including in-hospital mortality, the incidence of new-onset organ failure and new-onset persistent organ failure (respiration, cardiovascular and renal), receipt of new organ support therapy, requirement for drainage or necrosectomy, bleeding requiring intervention, human leucocyte antigens-DR(HLA-DR) on day 0, day 7, day 14, and so on and adverse events. Considering the possibility of readmission, an additional follow-up will be arranged 90 days after enrolment, and IPN and death at day 90 will also be served as secondary outcomes.Ethics and disseminationThis study was approved by the ethics committee of Jinling Hospital, Nanjing University (Number 2015NZKY-004-02). The thymosin alpha 1 in the prevention of infected pancreatic necrosis following acute necrotising pancreatitis(TRACE) trial was designed to test the effect of a new therapy focusing on the immune system in preventing secondary infection following ANP. The results of this trial will be disseminated in peer-reviewed journals and at scientific conferences.Trial registration numberClinicalTrials.gov Registry (NCT02473406).

The air disturbance (or airwake) resulting from the interaction of ship motion and air flow, has a significant effect on shipboard rotorcraft operations. It is essential to develop capabilities to accurately model the rotor/ship aerodynamic interactions which can subsequently be used to implement an efficient and accurate virtual dynamic interface (VDI) simulation. The aerodynamic interaction of the rotorcraft and ship involves the mutual interference between the rotors, fuselage and ship structure. The ship airwake produces unsteady loads on the helicopter as a result of shear layers and turbulence. Therefore modeling rotor/ship aerodynamic interaction requires a high fidelity approach due to complex physical mechanisms that drive the flow phenomena. The interactions between rotor and ship have known to be highly non-linear, therefore the airwake due to an isolated ship has different flow characteristics compared to the ship airwake in presence of a rotorcraft. Moreover the coupled airwake has a feedback effect on the rotor wake geometry and vorticity strength which creates a two-way coupling scenario. In this study, a methodology was developed to couple a CFD ship airwake solver with a viscous Vortex Particle Method (VPM) for rotor wake solution to study rotor/ship aerodynamic interaction. The CFD and VPM solvers were used to compute the time accurate ship airwake and rotor wake, respectively, from first principles. This coupling methodology is demonstrated for a helicopter ground effect study. The coupling simulations were subsequently run for helicopter performing shipboard operations. The simulations showed the complex interactions of ship airwake with rotor wake including the ground effect that rotor experiences in the vicinity of the deck.

Rotor-induced-flow modeling and prediction has been one of the central issues for rotorcraft performance, control, stability, loads, and vibration analysis for decades. Traditional singularity-based methods used in most current comprehensive rotorcraft analysis codes are limited by the potential flow assumption and thus have to rely on empirical formulations (e.g., vortex decay factor, vortex core size, etc.) to reach a solution. This paper discusses the development and validation of a viscous vortex particle model for modeling the complicated rotor wake vorticity transportation and diffusion. Instead of solving the viscous vorticity equations through numerical discretization over the flowfield grid, the vortex particle method addresses the solution through a Lagrangian formulation in which there is no artificial numerical dissipation involved. The Lagrangian approach also allows the application of the hierarchical TreeCode and the fast multipole method. These methods can dramatically improve the computational efficiency of the viscous vortex particle simulation, which enables it to be used for practical and comprehensive rotorcraft analysis.

In recent years, there has been significant interest in on-blade concepts that expand the operating envelope of helicopters without compromising the performance characteristics of the baseline rotor. The variable-droop leading-edge concept is explored in a modified version of the Navier-Stokes solver OVERFLOW. Modifications were made to the solver to allow deforming-grid capability. This concept was explored in dynamic stall tests of the VR-12 and SC1095 helicopter airfoils. The variable-droop leading-edge airfoils have dramatically reduced drag and moment rises associated with dynamic stall. Using the results of these tests, a modified UH-60A rotor incorporating variable-droop leading-edge airfoils was analyzed using loosely coupled computational fluid dynamics and comprehensive structural dynamics with OVERFLOW and DYMORE and compared with the standard UH-60A rotor for high-thrust-case flight 9017. Results show a reduction in the peak negative pitching moment. The rotor efficiency was shown to improve by 2.9% and the 4/rev component of vertical force reduced by 8%. These performance improvements can be improved with an improved droop schedule and by incorporating improved transonic airfoils.

Modeling and simulation are used to support a wide range of applications including design, analysis, operations research, test and evaluation, training, etc. Each application has different fidelity requirements and computational limitations. Consequently, a variety of models are required to support a single aircraft type throughout its life cycle. Validation and configuration management of this array of models is costly. FLIGHTLAB[Formula: see text]is a software tool that supports selective fidelity modeling and simulation to insure trace-ability and commonality between models, ranging from the comprehensive models required for design to the real time models required for training and hardware-in-the-loop testing. Providing a single tool with this range of modeling options greatly enhances the configuration management capability. Also once the highest fidelity, comprehensive, model is validated, it can be used to provide reference data for validation of simpler models, thereby expediting the validation process for all levels of modeling. This paper describes the real-time simulation capability of FLIGHTLAB[Formula: see text]models and their trace-ability to higher level FLIGHTLAB[Formula: see text]models.

Landing a rotorcraft on a moving ship deck and under the influence of the unsteady ship airwake is extremely challenging. In high sea states, gusty conditions, and a degraded visual environment, workload during the landing task begins to approach the limits of a human pilot s capability. It is a similarly demanding task for shipboard launch and recovery of a VTOL UAV. There is a clear need for additional levels of stability and control augmentation and, ultimately, fully autonomous landing (possibly with manual pilot control as a back-up mode for piloted flight). There is also a clear need for advanced flight controls to expand the operational conditions in which safe landings for both manned and unmanned rotorcraft can be performed. For piloted rotorcraft, the current piloting strategies do not even make use of the available couplers and autopilot systems during landing operations. One of the reasons is that, as the deck pitches and rolls in high sea states, the pilot must maneuver aggressively to perform a station-keeping task over the landing spot. The required maneuvering can easily saturate an autopilot that uses a rate limited trim system. For fly-by-wire aircraft, there is evidence that the pilot would simply over-compensate and negate the effectiveness of a translation rate command/position hold control mode. In addition, the pilots can easily over-torque the rotorcraft, especially if they attempt to match the vertical motion of the deck. This project seeks to develop advanced control law frameworks and design methodologies to provide autonomous landing (or, alternatively, a high level of control augmentation for pilot-in-the-loop landings). The design framework will focus on some of the most critical components of autonomous landing control laws with the objective of improving safety and expanding the operational capability of manned and unmanned rotorcraft. The key components include approach path planning that allows for a maneuvering ship, high performan

This paper describes a physics-based rotorcraft/ship aerodynamic interaction modeling method in support of real time flight simulation. The widely used Peters-He finite state dynamic wake model (Ref. 1 ) was augmented using the simulation results obtained from a first-principle based hybrid solver which couples a grid-free viscous Vortex Particle Method (VPM) with an unstructured CFD solver. The fully coupled VPM/CFD solution addresses the challenging rotorcraft/ship interaction problem and was shown to capture the physics of the mutual aerodynamic interactions between the rotor wake and the ship airwake disturbance. However, the VPM/CFD solution is too computationally expensive to support any real time simulation applications. The finite state dynamic rotor wake model, on the other hand, has already been routinely used in real time rotorcraft flight simulation. The augmented finite state dynamic wake model accounts for the physics of the rotor/ship mutual aerodynamic interactions and provides an accurate and efficient solution. The paper discusses the modeling methodology and the associated algorithms used to augment the finite state dynamic wake model via a coupled VPM/CFD solution. It was demonstrated that the augmented model accurately captures the essential physics of the rotorcraft/ship aerodynamic interaction and, at the same time, is computationally fast enough to support real time simulation.

In Part I of this two-part article, we developed a finite state induced flow model for a two-dimensional airfoil. In this second part, we develop a finite state induced flow model for the three-dimensional induced flow for a rotor. The coefficients of this model are found in a compact closed form. Although the model does not presuppose anything about the source of lift on the rotating blades, applications are given in which the Prandtl assumption is invoked. That is, the two-dimensional lift equations are used at each radial station, but with the inflow from the three-dimensional model. The results are shown to reduce (in several special cases) to Prandtl-Golds tein theory, Theodorsen theory, Loewy theory, dynamic inflow, and blade-element momentum theory. Comparisons with vortex-filament models and with experimental data in hover and forward flight also show excellent correlation.

This paper describes the investigation of the fundamental physics of rotor wake dynamics, including the essential properties of the rotor tip vortices, such as the trajectory, the core size, the circulation strength, etc. The paper also discusses the simulation of the challenging rotor aerodynamic interference problems using the state-of-the-art viscous Vortex Particle Method (VPM). In order to accurately model the complicated rotor wake problem, efforts were made to enhance the viscous vortex particle method, including the multi-resolution vorticity source generation, the VPM-VIC algorithm, and the far field boundary conditions. This paper also addresses the aerodynamic interaction to allow for the effects of the near field structures, such as the fuselage and the ship deck. Simulation results were compared with available measurements and excellent correlations were demonstrated.

This paper presents a hybrid fluid solver which couples a grid-free viscous vortex particle method with gridbased unstructured Computational Fluid Dynamics (CFD) solvers. The solver was developed to address the challenging rotor wake and aerodynamic interaction problem. The viscous vortex particle model is a state-of-the-art rotor wake modeling technology that can accurately solve for the complicated rotor wake variation while the unstructured Computational Fluid Dynamics (CFD) solvers can accurately predict the near-body flow. In this coupled solution, the vortex particle method is used to transport vorticity over the flow field while the Computational Fluid Dynamics (CFD) solvers are used to solve near-body flow and provide vorticity sources to the vortex particle method. The wake effect is fed back to the CFD solution to form a coupled solution. This paper discusses the fundamental aspects of the methodology and the associated algorithms that were used to couple the viscous vortex particle method and the unstructured CFD solvers. The developed hybrid tool was used to investigate the unsteady aerodynamic interactions between the helicopter rotor and body and excellent correlations between the simulation results and the measurements were achieved.

In this investigation, a robust and efficient unstructured Computational Fluid Dynamics(CFD) method is developed for rotorcraft aerodynamic interaction simulation. The advective upwind splitting method (ASUM+) with lowdiffusion flux-splitting scheme is implemented to achieve the robust simulation at all flow speeds. For rotorcraft simulation, the CFD is solved using an Eulerian framework and is only applied in the vicinity of rotor blades or fuselage surface to generate the particles and vorticity sources of the vortices. The evolution of these vortices is resolved by applying the vortex particle method with a Lagrangian framework in the rest of the flow field.

In this article, a rotor aeroelastic model based on a newly developed finite state dynamic wake, coupled with blade finite element analysis, is described. The analysis is intended for application in rotor blade design optimization. A coupled simultaneous system of differential equations combining blade structural dynamics and aerodynamics is established in a formulation well-suited for design sensitivity computation. Each blade is assumed to be an elastic beam undergoing flap bending, lead-lag bending, elastic twist, and axial deflections. Aerodynamic loads are computed from unsteady blade element theory where the rotor three-dimensional unsteady wake is described by a generalized dynamic wake model. Correlation of results obtained from the analysis with flight test data is provided to assess model accuracy.

This paper presents an analytical formulation of an optimum rotor interdisciplinary design. A finite-state aeroelastic rotor model, coupling simultaneously a generalized dynamic wake model with blade finite elements, is applied to perform the optimum rotor blade design for improved aerodynamic performance and vehicle vibration. A feasible direction nonlinear optimizer provides the optimization algorithm. The uniqueness of the present approach is the systematic rotor aeroelastic model, which offers an efficient analytical tool, and retains necessary aerodynamic and blade dynamic building blocks for a sufficient rotor dynamic response analysis. The formulation is well-suited for an efficient design sensitivity computation without resorting to finite differencing, and thus provides a practical design tool.

A helicopter is intrinsically interdisciplinary due to the close coupling among aerodynamics, dynamics, and the blade structural details. Therefore a design optimization with proper interactions among appropriate disciplines (such as structure, dynamics, and aerodynamics) can offer significant benefit to improve rotor performance. This paper studies the integration of structure, dynamics, and aerodynamics in design optimization of helicopter rotor blades. The optimization is performed to minimize the rotor power required and to satisfy design requirements from structure (minimum blade weight and safe stress margin and fatigue life) and dynamics (proper placement of blade natural frequencies and free of flutter). An effort is made to formulate an effective strategy for combining these various requirements in the optimization process. The paper also presents a way for an intelligent phasing of this interdisciplinary optimization to overcome the hurdles due to conflicting demands on the design variables which arise from different disciplines.

Rotorcraft shipboard landing is a challenging task that involves complicated aerodynamic and dynamic interaction between the aircraft, the ship dynamics, and the ship induced unsteady airwake. Good progress has been made in recent years in developing modeling and simulation technology to support shipboard rotorcraft testing and training. This paper reviews ART’s eorts in developing a high fidelity shipboard rotorcraft flight simulation system that integrates modeling, analysis, and real time flight simulation tools into a unified simulation system environment. The integrated simulation system provides a cost eective and high fidelity tool that enhances rotorcraft/ship testing and training. The shipboard rotorcraft modeling capability developed adequately models the dynamics of both the rotorcraft and the ship and addresses the complicated aerodynamic rotorcraft/ship interaction, including the strong influence of the unsteady ship airwake. The study of shipboard rotorcraft simulator fidelity concerns the improvement of the simulation in order to satisfy pilot subjective evaluation criteria and the eects of the simulator environment, including the visual cuing and the ship airwake hazard display, in order to assist the pilot during the shipboard landing task. The modeling complexity details for the major components including the aircraft model, the ship airwake, the ship motion, the component coupling, and the visual scene and their aects are discussed.

In recent years, there has been significant interest in on-blade concepts that expand the operating envelope of helicopters without compromising the performance characteristics of the baseline rotor. The variable-droop leading-edge concept is explored in a modified version of the Navier-Stokes solver OVERFLOW. Modifications were made to the solver to allow deforming-grid capability. This concept was explored in dynamic stall tests of the VR-12 and SC1095 helicopter airfoils. The variable-droop leading-edge airfoils have dramatically reduced drag and moment rises associated with dynamic stall. Using the results of these tests, a modified UH-60A rotor incorporating variable-droop leading-edge airfoils was analyzed using loosely coupled computational fluid dynamics and comprehensive structural dynamics with OVERFLOW and DYMORE and compared with the standard UH-60A rotor for high-thrust-case flight 9017. Results show a reduction in the peak negative pitching moment. The rotor efficiency was shown to improve by 2.9% and the 4/rev component of vertical force reduced by 8%. These performance improvements can be improved with an improved droop schedule and by incorporating improved transonic airfoils.

This paper discusses the development of the High Performance Computing (HPC) Collaborative Simulation and Test (CST) portfolio CST-03 program, one of the projects in the Common HPC Software Support Initiative (CHSSI) portfolio. The objective of this development was to provide computationally scalable tools to predict rotorcraft performance, stability, and control. The ability to efficiently predict and optimize vehicle performance, stability, and control from high fidelity computer models would greatly enhance the design and testing process and improve the quality of systems acquisition. Through this CHSSI development, the US Navy Test Pilot School performance, stability, and control test procedures were fully implemented in a high performance parallel computing environment. These Navy flight test support options were parallelized, implemented, and validated in the FLIGHTLAB comprehensive, multidisciplinary modeling environment. These tools were designed to interface with other CST compatible models and a standalone version of the tools (FLIGHTLAB-ASPECT) was delivered for use independent of the FLIGHTLAB development system. Tests on the MAUI Linux cluster indicated that there was over 25 times speedup using 32 CPUs. The tests also met the accuracy criteria as defined for the Beta trial.

Rotorcraft air vehicle flight testing is required to determine how well the aircraft will perform in selected operational scenarios. The actual air vehicle flight test program may require extensive planning, instrumentation, flight testing, data analysis, and reporting. Considerable emphasis has been placed on working to reduce the cost and cycle time associated with conventional flight testing. One option with the potential to help reduce the cost and cycle time of air vehicle flight testing involves using credible simulation. Although numerous simulation models exist, very few have the capability to duplicate the flight test techniques taught at the US Navy Test Pilot School (USNTPS). With dedicated research and development, these classic flight test techniques have been implemented into a generic analytic model structure. The analytic model structure can be operated on a personal computer with a Linux operating system. The time required to run a complete analytic rotorcraft air vehicle flight test program can be overnight or much longer depending on the parameter variations selected for the specific computer run. A goal is to be able to use the analytic options to show how close the projected flight test matrix flight conditions approach flight limits. Another goal is to be able to show the sensitivity of selected flight test parameters while the test plan is being developed. A recent High Performance Computing (HPC) portfolio on Collaborative Simulation and Testing (CST) was established to help integrate analytic options to enhance flight testing. The CST-03 topic focuses on developing parallel processing options to greatly speed up the analytic ability to predict rotorcraft performance, stability, and control

Work is ongoing to develop a web-based capability to support flight testing and mishap investigations. Fewer new aircraft are being procured today compared to aircraft procurement a couple decades ago. As the older members of the test force retire or change jobs, more pressure is placed on the more junior engineers to conduct the testing. Flight test training is accomplished at government and commercial test pilot schools, but after graduating the flight test engineers and pilots must primarily work with on-the-job training. One approach to improve flight test training support, currently being developed as part of a small business innovative research program, involves combining advanced technology programs associated with a physics-based analysis model structure and the World Wide Web. This paper discusses the results of the ongoing program to enhance and integrate an advanced simulation model structure with a collaborative network and with advanced microprocessors.