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In aerospace engineering, there are several control systems affected by dry friction, which are characterized by low inertia and high working frequencies. For these systems, it is possible to use a downgraded, first-order dynamic model to represent their behaviour properly without run into numerical problems that would be harmful for the solution itself and would require high computational power to be solved, which means more weight, costs, and complexity. Yet, the effect of dry friction is still possible to be accounted for accurately using a new algorithm based on the Coulomb friction model applied to the downgraded, first-order dynamic model. In this paper, the degraded first-order model is applied to an electrohydraulic servomechanism with its PID control unit, hydraulic motor, electrohydraulic servo-valve, and applied load. These components represent a classic airplane actuator system. The downgraded model will be compared to the second-order one focusing on the pros and cons of the reduction process with a focus on the effect of dry friction for reversible and irreversible actuators.

The steady-state approaches traditionally used to assess the capacity of overhead transmission power lines are being progressively replaced by procedures that consider the real and extremely variable weather conditions that are present along the path of the line under analysis (Dynamic Thermal Rating). Dynamic Thermal Rating (DTR) does not just estimate the temperature of the conductor in the different spans of the line, but also some mechanical quantities like their tension and sag, in order to appreciate the limitations imposed by the constraint of the minimum ground clearance. Modern DTR procedures need, therefore, proper mechanical models of the lines, in order to assess what happens both in normal and fault conditions. This paper proposes a comparison between a Finite Element Method (FEM) and a novel lumped-parameter model implemented through the Modelica language. Different realistic scenarios have been considered, like gusts of wind and the presence of ice. The outcomes of the two dynamic models have been compared to identify a trade-off between the accuracy of results and the computational time, as well as the dependency on the number of lumped masses used to model the line.

The development of a zero-dimensional model for analysing pressure phenomena in multiple stage external gear pumps is addressed in the present work. The tandem pump is composed of two coaxial stages: the high pressure one, made by spur gears, and the low pressure one, made by helical gears. The two stages have common shafts and a common case. The oil pressure course around the gearpair, as well as the suction/delivery pressure ripple, is estimated for both stages. Attention is focused on the description of the modelling approach: an original method is developed to model the helical gears and their effects on the determination of the geometrical parameters. The lumped parameter (LP) model takes advantage of a Computational Fluid Dynamic (CFD) model applied to different pump regions in order to estimate several internal flow features. Measured delivery pressure ripple and volumetric efficiency are used to evaluate the model reliability under different working conditions.

The U values assumptions for construction components represent a significant source of uncertainty when estimating the energy performance of buildings. This uncertainty affects decision-making processes in multiple ways, from policy making to design of new and refurbished buildings. The correct estimation of both static (e.g. thermal transmittance) and dynamic thermal properties is crucial for quality assurance in building performance assessment. Further, while today many sophisticated simulators are available for building performance modelling, lumped parameter models can help reducing computational time for parametric simulation or optimization and enable inverse estimation of lumped thermal characteristics. A lumped parameter approach for construction components is proposed, for example, by the ISO 52016-1:2017 norm, introducing simplifications that are intrinsically dependent on component’s stratigraphy. This approach complements ISO 13786:2017 norm method, which is limited to steady-state periodic temperature and heat flux boundary conditions. In this research we consider these two different approaches, detailed and lumped modelling, comparing them first in idealized conditions and then in experimental conditions to analyse the robustness of methods.

Highly detailed computer models are required for design and development of modern flight control systems, capable of emulating with high accuracy the behaviour of on-board equipment. At the same time, different simplified models are needed, specifically intended for operations such as the optimization of preliminary design and the development of diagnostic or prognostic strategies. These simplified models are required to combine sufficient levels of accuracy and reliability with reduced computational costs, to minimize the computational burden associated with prognostic and optimization algorithms. In this work, we focus on electro-hydraulic actuators, since they are critical subsystems in terms of safety and availability of the aircraft. Advanced monitoring and prognostic algorithms require new numerical models, combining an acceptable computational effort with a satisfying ability to simulate their performance and dynamics. To this purpose, this paper proposes a new simplified numerical model of the servovalve fluid-dynamic behaviour. This numerical algorithm, based on a very compact semi-empirical formulation, is intended to take into account in a simplified but sufficiently accurate way several typical effects related to the SV spool geometry and the operating conditions. To evaluate the approximations introduced by this model into a system-level simulation, it has been integrated into a dedicated numerical model simulating a simple electrohydraulic on-board actuator, and compared with a higher fidelity servovalve model.

Some specific applications fields of electric motors, such as Food and Beverage (F&B) applications, require highly demanding hygiene procedures that involve a highly aggressive environment for the motor, including e.g. frequent high pressure and high temperature washing with water or more aggressive detergents. Specific materials and protection features are used in motors to better withstand such environment, however these have an impact on performance and lead to oversized machines. This paper describes some solutions and their impact on performance, with specific focus on the thermal properties of the analyzed machine.

Made available in DSpace on 2018-12-11T17:25:02Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-04-01 Voltages and currents in the transmission line are described by differential equations that are difficult to solve due soil and skin effect that has to be considered for accurate results, but it increases their complexity. Therefore there are some models to study the voltages and currents along in transmission line. The distributed parameters model that transforms the equations in time domain to the frequency domain and once the solutions are obtained, they are converted to time domain using the Inverse Laplace Transform using numerical methods. Another model is named lumped parameters model and it considers the transmission line represented by a π-circuit cascade and the currents and voltages are described by state equations. In the simulations using the lumped parameters model, it can be observed the presence of spurious oscillations that are independent of the quantity of π-circuits used and do not represent the real value of the transient. In this work will be projected a passive low-pass filter directly inserted in the lumped parameters model to reduce the spurious oscillations in the simulations, making this model more accurate and reliable for studying the electromagnetic transients in power systems. Universidade Estadual Paulista (UNESP) Universidade Estadual Paulista (UNESP)

The article gives a general description of the SIMCO calculation code designed to simulate thermohydraulic and physico-chemical processes in containments of nuclear power facilities. The authors present a calculation technique based on a physico-mathematical model in lumped parameters. As a numerical solution method, the modified semi-implicit SIMPLER procedure is used. The code was examined using analytical and qualitative tests. A comparison of the numerical and analytical solutions showed good agreement. The code was verified using the experimental data obtained at the NUPEC installation (Japan). Based on the results of testing and verification, it was concluded that, in general, physico-mathematical code models adequately describe the processes of heat/mass transfer in the containment. Therefore, this SIMCO code version can be used to analyze the totality of thermophysical and physico-chemical processes in nuclear power facilities with containments, including the transfer of hydrogen/steam/air mixtures.

Short-time thermal transient identification method was successfully adopted to evaluate the slot thermal parameters of induction motors for industry applications. In this work, the modeling approach and the identification methodology are extended to the more sophisticated case of multiple three-phase machines. The generalized model takes into consideration the mutual heat exchange between the windings as well as the possible causes of temperature mismatch. A complete procedure to evaluate the parameters of the modified model is provided, supported by experimental validation on a 7.5 kW machine with two three-phase winding in contact at slot level. The method covers any type of multiple three-phase machines, whatever the thermal promiscuity of the winding sets: from deep coupling as the ones presented, to the case where only the end-turns are in contact, to the completely decoupled case. The proposed technique can be useful for the machine design and for real-time temperature monitoring during operation.

This paper presents mathematical modeling and numerical simulation results for a miniature, planar, spiral transformer (MPST) fabricated in micro-electromechanical MEMS technology. When the MPST is magnetic nanofluid cored, magnetization body forces occur, entraining it into a complex flow. This particular MPST design is then compared with other competing solutions concerning the lumped (circuit) parameters. Finally, the heat transfer problem is solved for different electromagnetic working conditions to assess the thermal loads inside the MPST.

This study presents an analytical model of the dynamics of an axisymmetric liquid bridge confined between two circular pads and subjected to small vertical periodic perturbations. Such system finds important applications in microassembly and microjoint design, where force and damping need to be precisely controlled. The liquid bridge is modelled by an equivalent spring/dashpot/mass system characterised by the spring constant k, the damping coefficient b and the equivalent mass m, respectively. An abacus for k as well as analytical approximations for k, b and m based on simplifications of the Navier–Stokes equation are provided. The study is validated by experiments and numerical simulations of the system. We describe the experimental setup we designed to investigate vertical forces arising on the bottom pad from small periodic perturbations of the top pad confining the liquid meniscus. The setup allowed the accurate control of all physical and geometrical parameters relevant for the experiments. The parameters we investigated are both physical (viscosity and surface tension of the fluid) and geometrical (the edge angle between the meniscus and the pad, the height of the meniscus). The good agreement between model predictions and results let us conclude that k, b and m involve only one physical property of the liquid, namely the surface tension, the viscosity and the density, respectively.

The potential advantage of using superconducting materials in electrical devices is well described in the literature. The electromagnetic properties of these materials make them unique for several applications, such as, e.g. electrical machines and drives, fault current applications, or superconducting magnetic energy storage. In the development of electromechanical conversion devices, superconducting materials are used foreseeing mainly a decrease in the device dimensions or a performance improvement for the same active volume. To guarantee a good application of this kind of materials it is important to describe and model the phenomena that characterize their operation under different regimes. In this paper, a study based in FEM simulations of a motor with bulk superconductor in the rotor is carried out, with the purpose of understand, quantify and qualify which phenomena are present in the different regimes of the motor, leading to obtaining an equivalent electrical circuit with lumped parameters.

In the last years the use of high temperature low sag conductors has become more and more frequent in electric power system. Such conductors have an inner layer in polymeric and/or fibre material, with reduced thermal coefficient and weight with respect to conventional ones. For this reason, under short circuit conditions they can experience large displacements due to the electromagnetic forces induced by the fault currents. Such displacements can influence phase-to-ground or phase-to-phase clearances, thus reducing the system security. In this paper, a possible way to model the dynamic electromechanical behaviour of overhead electric power lines conductors is presented and discussed, using lumped parameter models implemented through Modelica language.

Zbog svoje važnosti za elektroenergetski sustav, transformatori se projektiraju kako bi, uz stacionarne, bili u mogućnosti izdržati i situacije mogućih prijelaznih stanja u električnoj mreži. Zbog toga postoji potreba za kvalitetnim visokofrekvencijskim modelom namota transformatora. Ova disertacija se bavi izradom nadomjesnog visokofrekvencijskog modela namota transformatora pomoću metode koncentriranih parametara. Prikazana metodologija se zasniva na internom modelu te nastoji predvidjeti raspodjelu napona duž namota uslijed brzorastućih prijelaznih pojava. Svi parametri modela su određeni korištenjem numeričkih metoda zasnovanih na metodi momenata. Nadomjesni model namota je analiziran u vremenskoj i u frekvencijskoj domeni. Prikazana je metodologija određivanja raspodjele napona duž namota te proračun rezonantnih frekvencija namota transformatora. Model je verificiran mjerenjima na posebno konstruiranom modelu transformatora. Utvrđena je zadovoljavajuća točnost prikazanog nadomjesnog modela te mogućnost određivanja rezonantnih frekvencija namota i naponskih naprezanja duž namota. Transformers are vital to every electric power system. Due to various switching operations and atmospheric discharges, they are exposed to numerous overvoltages and have to be designed to correctly operate in those circumstances. Therefore, adequate mathematical models are needed to study their behavior at voltages with high frequency components. This dissertation presents the methodology for obtaining the high frequency model of transformer windings. The model is of internal type and is based on lumped parameters. All the parameter values are obtained using numerical methods based on the method of moments. Obtained transformer model is analyzed both in time and in frequency domain. The winding’s internal overvoltage distribution and the winding’s resonant frequency analysis is presented. Experimental verification of the developed numerical model has been done on a specially constructed transformer. Measurements are in a good agreement with calculated results.

Balıkesir Üniversitesi, Fen Bilimleri Enstitüsü, Elektrik-Elektronik Mühendisliği Ana Bilim Dalı, Anahtarlama olayları ve yıldırım, transformatör sargı uçlarında bir darbe geriliminin oluşmasına neden olmaktadır. Bu darbe geriliminin sargılardaki etkisinin incelenmesi için IEC 60076-3 standartında tanımlanan, 1,2 µs’de tepe değerine, 50 µs’de ise yarılanma değerine ulaşan bir sinyal, test esnasında transformatörlere uygulanır. Sargılar arasındaki yalıtkan malzemenin kapasitif davranışı ve sargıların endüktif özelliği nedeniyle, bu darbe gerilimi sargılarda yüksek frekanslı akımlar akmasına neden olur. Anma frekansında çalışan transformatör sargılarındaki gerilim dağılımı doğrusal iken, darbe gerilimi sonucu sargılarda oluşan yüksek frekanslı gerilimlerin dağılımı doğrusal değildir. Doğrusal olmayan gerilim dağılımı nedeniyle sargılar içerisinde öngörülemeyen noktalarda gerilim zorlanmaları meydana gelmesi ve bu nedenle sargı yalıtkanının zarar görmesi mümkündür. Darbe gerilimine karşı dayanımı yüksek transformatörlerin imal edilebilmesi için, tasarım aşamasında aşırı gerilimlere maruz kalan bölgelerin bilinmesi gerekmektedir. Yağlı tip transformatörlerin darbe gerilimi dağılımına ilişkin yeterince çalışma yapılmasına rağmen, kuru tip transformatörlerin darbe gerilimi dağılımına ilişkin yeterince çalışma bulunmamaktadır. Enerji sektöründe gittikçe büyük bir pazara sahip olmaya başlayan kuru tip transformatörlerin darbe gerilimi dağılımı bu çalışmanın konusunu oluşturmaktadır. Çalışma kapsamında, her bir fazı, yuvarlak, yassı ve strip olmak üzere, 3 farklı iletken ile sarılmış, 3 fazlı kuru tip transformatörün gerilim dağılımı analizi için sistemin matematiksel modeli oluşturulmuş ve parametreleri hesaplanmıştır. Modeli oluşturulan transformatör prototipi BEST Transformatör Tesisleri’nde üretilerek, benzetim sonuçlarının doğruluğu deneysel sonuçlarla karşılaştırılmıştır. Çalışma sonucunda, yassı iletkenli tipin sargıları arasındaki gerilim dağılımının diğer iki tipe göre daha düzgün olduğu ve en düşük aşım değerinin de bu tip tasarımda oluştuğu gözlenmiştir., Switching operations and lightning cause an impulse voltage on terminal of transformer windings. A signal whose peak time is 1,2 µs and half time is 50 µs according to IEC 60076-3 is applied to transformer windings during a test to investigate the effects of this situation. This impulse voltage causes to flow of current with high frequencies because of capacitive properties of insulation materials and inductive properties of windings. Altough voltage distribution of transformer windings running nominal frequency is linear, voltages distribution for high frequencies is nonlinear when impulse voltage is applied to transformer windings. Because of the nonlinear voltage distribution, there may be unexpected high potential differences between windings, and cause the corruption of insulation material. To produce a transformer having high capability to withstand impulse voltage, which sections of windings occur at high voltage must be known during design of transformer. Despite many studies have been done about impulse voltage distribution of oil type transformer, there aren't enough studies about dry type transformer. Impulse voltage distribution of dry type transformer which has increasing marketing share in energy industry is the topic of this study. In this study, dry type transformer having there different types of conductors which are round, flat and strip on high voltage sides is analysed. Mathematical model of the system has been established and parameters of the windings have been calculated for each phase of the transformer. Prototype of the transformer modelling for analysis has been produced by BEST Transformer company. Accuracy of the simulation model has been checked with experimental results. As a result of this study, the winding with flat conductor has better impulse voltage distribution and lower over voltage values than other two windings., Bu tez çalışması Balıkesir Üniversitesi, Bilimsel Araştırma Projeleri Birimi tarafından 2014 / 136 ve Balıkesir Elektromekanik Sanayi Tesisleri tarafından 124 proje numarası ile desteklenmiştir.

Mechanical structures often consist of active and passive parts, the former containing the sources, the latter the transfer paths and the targets. The active and passive parts are connected to each other by means of links. In this paper, an innovative theoretical model has been developed to achieve the mathematical decoupling of such structures without disassembling the substructures, when the links connecting the structures are resilient enough. This procedure is required to identify components causing a specific Noise, Vibration and Harsh-ness (NVH) problem. The links are regarded as a parallel connection of springs and dampers, ignoring some physical properties. However, the new procedure will provide a powerful construction in which different link models can be investigated. Therefore, this procedure will be called the Link-Preserving, Decoupling Method (LPD method). The absence of a time-consuming physical decoupling procedure distinguishes the LPD method from all known methods such as the classical TPA method. The LPD method is validated by two numerical simulations using linear and nonlinear lumped parameter models and by an experimental case study.

In an intrabody communication (IBC) system the human body is used as a part of a communication channel between the transmitters and receivers placed on the surface of the skin, in its vicinity, or implanted inside the user’s body. IBC systems use lower frequency band than standard wireless systems, and they have lower power consumption and lower range. Possible applications of IBC technology are broad: from biotelemetry and medicine to the communication between various electronic devices and security systems. This doctoral thesis is focused on analysis and modelling of a transmission path of an intrabody communication system, and on the design of very low power transmitters and receivers. Transmission characteristic of the capacitive IBC system depends on the tissue characteristics and signal path, defined by the positions of the transmitter and receiver, placement of the transmitter and receiver electrodes on the body, and surrounding environment. A procedure proposed for measuring IBC channel transmission characteristic in the frequency range from 100 kHz to 100 MHz provides galvanic decoupling of the measuring equipment from the IBC channel. Using a proposed measurement procedure, the influences of the type, size, and position of the transmitter and receiver electrodes, and the influence of the environment were investigated and theoretically explained. The conclusions were confirmed by the in vivo measurements in a realistic communication scenario, on a larger number of test subjects with different anatomical characteristics, for several static and dynamic body positions. Employing the measurement results analysis, a model of a capacitive intrabody communication system operating at discrete frequencies up to 100 MHz, based on lumped parameters and transmission lines was created. The guidelines for IBC transmitter and receiver design, optimal in the sense of power requirements, signal transmission quality, and dimensions were given, based on the developed model and in vivo measurements. Finally, the results of this thesis were applied in the development of an operating IBC system prototype. Sustavi za prijenos signala ljudskim tijelom (engl. intrabody communication, IBC) koriste čovjeka kao dio komunikacijskog kanala između odašiljača i prijamnika smještenih na površinu tijela, u neposrednu blizinu tijela, ili implantiranih unutar tijela korisnika. IBC sustavi rade na nižim frekvencijama nego standardni bežični sustavi i sukladno tome imaju manju potrošnju i manji domet. Moguće primjene IBC tehnologije su vrlo široke: od biotelemetrije i medicine s jedne strane do komunikacije između različitih elektroničkih uređaja i sigurnosnih sustava s druge strane. Ova doktorska disertacija se bavi analizom i modeliranjem prijenosnog puta kapacitivnog sustava za prijenos signala ljudskim tijelom, te razvojem odašiljača i prijamnika vrlo niske potrošnje. Prijenosna karakteristika IBC sustava ovisi o svojstvima tkiva i putu signala definiranom položajem odašiljača i prijamnika, načinom spajanja odašiljačkih i prijamnih elektroda na tijelo, te karakteristikama okoline. Postupak mjerenja prijenosne karakteritike IBC sustava u frekvencijskom području od 100 kHz do 100 MHz omogućava galvansko odvajanje mjerne opreme od IBC sustava. Tim postupkom su ispitani utjecaji tipa, vrste i položaja odašiljačkih i prijamnih elektroda, te utjecaj bliže okoline, koji je i teoretski objašnjen. Zaključci su potvrđeni in vivo mjerenjima provedenim u realnim uvjetima na većem broju ispitanika različitih anatomskih obilježja, za nekoliko statičkih i dinamičkih položaja tijela. Definirane su smjernice za izbor radne frekvencije i izlazne snage odašiljača te osjetljivosti prijamnika, temeljene na razvijenom modelu i provedenim mjerenjima. Rezultati istraživanja su primijenjeni prilikom razvoja prototipa kapacitivnog sustava za prijenos signala ljudskim tijelom.

Αναπτύσσεται ένα πλήρες δυναμικό μοντέλο μετασχηματιστή που λαμβάνει υπόψη τη γεωμετρία του πυρήνα και τη συνδεσμολογία των τυλιγμάτων. Το μοντέλο μπορεί εύκολα να ενσωματωθεί στις καταστατικές εξισώσεις ενός συστήματος ισχύος με σκοπό τη μελέτη της δυναμικής του απόκρισης και τον υπολογισμό ανωτέρων αρμονικών. Ο βρόχος υστέρησης του υλικού του πυρήνα εισάγεται με το μοντέλο που: (α) προτείνει ο Tellinen και (β) προτείνουν οι Jiles και Atherton. Τα μοντέλα αυτά υπολογίζουν σωστά τις απώλειες υστέρησης του πυρήνα, επιτρέποντας στα διάφορα τμήματα του πυρήνα να διαγράφουν διαφορετικούς βρόχους. Η επίδραση των δινορευμάτων ενσωματώνεται στο μοντέλο με μη γραμμικές ωμικές αντιστάσεις για τον υπολογισμό των οποίων αξιοποιούνται οι σχετικές με τα δινορεύματα, ευρέως αποδεκτές, εργασίες του Bertotti. Ο πίνακας Ld των αυξητικών επαγωγών του μετασχηματιστή υπολογίζεται για οποιαδήποτε γεωμετρία πυρήνα και αριθμό τυλιγμάτων με την βοήθεια του Ισοδυνάμου Αυξητικού Κυκλώματος (ΙΑΚ) του πυρήνα. Ο αναλυτικός υπολογισμός των στοιχείων του πίνακα Ld αναδεικνύει τον τρόπο εξάρτησης των αυξητικών επαγωγών του μετασχηματιστή από τη γεωμετρία του πυρήνα και από τη χαρακτηριστική καμπύλη του υλικού. A dynamic and complete transformer model is developed which takes into account the magnetic core geometry and the windings connections. This model can easily be incorporated with the state equations of a power system, in order to calculate its dynamic response and the harmonic content. The magnetic hysteresis of the core material is introduced the model that is proposed by: (a) Tellinen and (b) Jiles and Atherton. These models can estimate the hysteresis power losses even when the hysteresis loops into several parts of the core differ. The eddy currents effects are incorporated into the model by non-linear ohmic resistances which are based on Bertotti’s work for the eddy currents. The matrix Ld of the incremental inductances of the windings is calculated, for any possible core geometry and number of windings, using the Equivalent Incremental Circuit (EIC) of the core. The analytical calculation of the elements of the matrix Ld shows the dependency of the incremental inductances on the core geometry and the characteristic curve of the core material.

En este trabajo se estudia la influencia de parámetros concentrados sobre los modos normales de oscilación de un medio continuo de dimensiones finitas. En particular, se estudian las vibraciones de una antena dipolo corta con una inductancia concentrada y los modos acústicos en un tubo con una cámara de expansión en su punto medio. Se encuentra que estos problemas presentan una gran similitud con los modos transversales de una cuerda homogénea, fija en sus dos extremos y cargada con una masa en su punto medio. In this work, the influence of lumped parameters on the normal oscillation modes of mechanical systems are studied theoretically. In particular, we study the vibration modes of a dipole antenna with concentrated inductances and a tube with an expansion chamber inserted in its middle point. It is found that these problems have close similarities with the transverse modes of a homogeneous string fixed at both ends and loaded with one mass at its middle point.

We present a low power analog adaptive equalization technique suitable for combating inter-symbol-interference at very high data rates. The proposed technique, which we term the lumped parameter equalizer, addresses several of the problems associated with conventional microwave equalizers based on the tapped delay line structure. The theory is given, and simulation results comparing it with the performance of ideal tapped delay line filters are shown. Circuit implementations are discussed, along with the effect of nonidealities on equalizer performance. � 2008 IEEE.

Hemodynamic instability, mostly due to vertical lifting of the heart, is usually observed during beating-heart surgical procedures. However, some hemodynamic parameters, such as coronary blood flow, are not routinely measured. A digital computer model of the circulation able to simulate and analyze the effects of heart lifting and the Trendelenburg maneuver, and thus supply detailed hemodynamic information to the clinicians would provide a useful analytical tool. A lumped parameters model of the circulation was applied to both beta-blocked and not beta-blocked pigs. The results confirmed a drop of cardiac output and coronary flow during heart lifting and a rise of both variables after the Trendelenburg maneuver for beta-blocked animals. In not beta-blocked pigs, the analysis was more complex but the model reproduced experimental data and permitted coronary flow to be estimated. These results showed the feasibility of numerical simulation for specific circulatory conditions encountered during beating-heart surgery.

Electro Thermo Mechanical (ETM) actuators play important role in rapidly growing MEMS area, particularly as a part of the more complex MEMS assemblies. Compared to the other types of micro actuators, ETM actuators generate large force with the price of the high power consumption. Tradeoff between these two properties, and design requirements arise necessity for the development of its accurate dynamical mathematical model. The accurate model leads towards the optimal design and, if necessary, can be used for a subsequent design of control algorithms. In general, the mathematical model consists of the three sub-models-electrical, thermal and mechanical and is should be considered as multi-physics phenomena with thermal one playing a dominant role. The dynamics of particular sub-model is determined by combining of the theoretical and Finite Element Analysis approach, verified with the available experimental data. Simultaneous application of these three approaches requires a definition of a procedure that leads toward determination of the model. In this paper, mentioned procedure is described in details, and is subsequently illustrated on the example of two hot arm bimorph thermal actuator fabricated using Poly-Multi User MEMS Process (PolyMUMPs).

Deep water, Gibson soil, Homogeneous (water saturated porous) isotropic elastic half-space. Compressible versus incompressible strata. Low frequency versus high frequency factors.

Deep water, Gibson soil, Homogeneous (water saturated porous) isotropic elastic half-space. Compressible versus incompressible strata. Low frequency versus high frequency factors.

This work describes a lumped parameter mathematical model for the prediction of transients in an aerodynamic circuit of a transonic wind tunnel. Control actions to properly handle those perturbations are also assessed. The tunnel circuit technology is up to date and incorporates a novel feature: high-enthalpy air injection to extend the tunnel’s Reynolds number capability. The model solves the equations of continuity, energy and momentum and defines density, internal energy and mass flow as the basic parameters in the aerodynamic study as well as Mach number, stagnation pressure and stagnation temperature, all referred to test section conditions, as the main control variables. The tunnel circuit response to control actions and the stability of the flow are numerically investigated. Initially, for validation purposes, the code was applied to the AWT ("Altitude Wind Tunnel" of NASA-Lewis). In the sequel, the Brazilian transonic wind tunnel was investigated, with all the main control systems modeled, including injection.