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The regular reflection of oblique steady and unsteady shocks in a perfect gas is considered. Non-monotonic variation of the mechanical and thermal loads on the obstacle with respect to shock/blast wave incidence angle is shown; the obstacle slope angles that correspond to pressure and temperature minima downwards of both steady and unsteady shock reflection point are determined analytically. Achieved minimization of dynamical and thermal loads at shock/blast wave reflection can be of use in space flight safety problems as blast safety onboard a spaceship, protection of spaceport facilities from blast of rocket carrier, prevention of fire onboard, and stable functioning of rocket engines, including ones based on detonation effects.

The propagation of cylindrical shock wave generated by a moving piston in a self-gravitating perfect gas in the presence of axial or azimuthal magnetic field with monochromatic radiation in rotating medium is investigated. The gravitational effect of the gas is taken into consideration. It is considered that the radiation flux moves through electrically conducting self-gravitating perfect gas with variable density and the energy is absorbed only behind the shock which moves in the direction appositive to the radiation flux. The results are discussed by comparing self-gravitating and non-gravitating gas, rotating and non-rotating medium, with or without magnetic field. The effects of variations of Alfven–Mach number, rotational parameter, gravitational parameter, adiabatic exponent and variation of piston velocity index are discussed in detail. The increase in magnetic field strength, adiabatic exponent and gravitational parameter have decaying effect on shock wave. It is shown that the shock wave is stronger with axial magnetic field and weaker with azimuthal magnetic field.

In this paper, a study concerning strong plane and cylindrically symmetric shock waves in a dusty gas atmosphere under isothermal condition has been performed, by taking into account the power series expansion method. The flow medium is assumed to be a mixture of perfect gas and small solid particles. The governing equation and associated boundary conditions are non-dimentionlized using a similarity transformation, and are hence expanded as a power series in $${\mathrm{M}}^{-2}$$ , where $$\mathrm{M}$$ is the upstream mach number. Runga-Kutta method of order four has been used to obtain a numerical solution. The effect of (i) geometry factor and (ii) dust loading parameters on the flow variables behind the shock front has been studied in detail and their behaviour in flow field is illustrated via figures. It has been observed that the in the flow field region the quantity $${\mathrm{J}}_{0}$$ increases with increase in $$\mathrm{G}$$ (the ratio of density of solid particles to the initial density of perfect gas) while it decreases with increment in $${\upkappa }_{\mathrm{p}}$$ (mass concentration of solid particles) and $$\mathrm{j}$$ (geometry factor). Hence, $${\upkappa }_{\mathrm{p}}$$ has a decaying effect on shock wave, whereas the shock grows with increment in $$\mathrm{G}$$ and $$\mathrm{j}$$ .

The influence of high-temperature effects on the stability of the wake behind a cuboidal roughness element is presented. Different flow assumptions are considered, including a calorically perfect gas, a thermally perfect gas and a mixture of gases in chemical non-equilibrium. Two-dimensional linear stability (2D-LST) computations are performed along the roughness wake for each of the different flow models and compared. The results show that, in the vicinity of the roughness element, the sinuous perturbation is stabilized by the excitation of the vibrational energy mode, whereas the varicose disturbance presents a strong destabilization. Further downstream, the sinuous instability is found to decay at a slower rate when accounting for vibrational excitation in its modeling, yielding a higher integrated amplification factor than with a calorically perfect gas assumption., info:eu-repo/semantics/published

Numerical simulations of 3-D disturbances induced by an underexpanded jet in supersonic crossflow (JISC) in the Mach 5.4 flat-plate boundary layer (BL) are carried out. The Navier–Stokes equations for compressible perfect gas are integrated using the in-house solver implementing an implicit finite-volume shock-capturing scheme with the second-order approximation in space and time. The numerical solutions indicate that the wall normal injection through a circular hole forms an underexpanded jet of barrel shape, which induces a system of vortices propagating downstream. These vortices are destabilized at a short distance that leads to rapid nonlinear breakdown and formation of a turbulent wedge. The vortex structure, its instability and breakdown to turbulence resemble those induced by an isolated roughness element. It is shown that the normal wall injection effectively trips the BL flow. This encourages further numerical studies of active tripping of high-speed BL flows using rows of JISC.

The effect of finite-rate internal energy transfer on shock interaction mechanisms of CO2-dominated flows is investigated. The polyatomic molecule has a relatively low characteristic vibrational temperature that causes vibrational degrees of freedom to be excited across a shock wave at hypersonic regimes. In this paper, the impact of accounting for the time associated to the relaxation of this process, as opposed to assuming instant thermal equilibrium, on the shock structures occurring in the flowfield over a double-wedge geometry is numerically studied. A Mach 9 flow over two different geometries is simulated with two different models, the two-temperature model of Park and the thermally perfect gas model. Simulations are carried out with the SU2 software that is coupled to the Mutation++ library, providing thermodynamic, chemical kinetic and transport properties of any mixture of gases for a given state of the flow. Anisotropic mesh adaption is used with the AMG library to accurately capture highly directional and high-gradient localized flow features. Results show that different ways of modelling the effect of vibrational relaxation have a major impact on the size of the compression corner separation bubble, leading to different shock wave systems in this region. As a consequence, the obtained shock interaction mechanisms differ as well. The shock patterns obtained for the thermally perfect gas model result in stronger impingement on the surface and higher aerodynamic loads of pressure and heat flux.

In an attempt to investigate the structures of ultra-relativistic jets injected into the intracluster medium (ICM) and the associated flow dynamics, such as shocks, velocity shear, and turbulence, we have developed a new special relativistic hydrodynamic (RHD) code in the Cartesian coordinates, based on the weighted essentially non-oscillatory (WENO) scheme. It is a finite difference scheme of high spatial accuracy, which has been widely employed for solving hyperbolic systems of conservation equations. The code is equipped with different WENO versions, such as the 5th-order accurate WENO-JS (Jiang & Shu 1996), WENO-Z, and WENO-ZA, and different time integration methods, such as the 4th-order accurate Runge-Kutta (RK4) and strong stability preserving RK (SSPRK), as well as the implementation of the equations of state (EOSs) that closely approximate the EOS of the single-component perfect gas in relativistic regime. In addition, it incorporates a high-order accurate averaging of fluxes along the transverse directions to enhance the accuracy of multi-dimensional problems, and a modification of eigenvalues for the acoustic modes to effectively control the carbuncle instability. Through extensive numerical tests, we assess the accuracy and robustness of the code, and choose WENO-Z, SSPRK, and the EOS suggested in Ryu et al. (2006) as the fiducial setup for simulations of ultra-relativistic jets. The results of our study of ultra-relativistic jets using the code is reported in an accompanying paper (Seo et al. 2021, Paper II)., 21 pages, 10 figures, accepted for publication in ApJ

In a recent publication, Hornung et al. (J. Fluid Mech., vol. 871, 2019, pp. 1097–1116) showed that the shock wave stand-off distance and the drag coefficient of a cone in the inviscid hypersonic flow of a perfect gas can be expressed as the product of a function of the inverse normal-shock density ratio ε and a function of the cone-angle parameter η, thus reducing the number of independent parameters from three (Mach number, specific heat ratio and angle) to two. Analytical forms of the functions were obtained by performing a large number of Euler computations. In this article, the same approach is applied to a symmetrical flow over a wedge. It is shown that the same simplification applies and corresponding analytical forms of the functions are obtained. The functions of ε are compared with the newly determined corresponding functions for flow over a circular cylinder.

This thesis concerns a technical hurdle that must be overcome in relation to air-breathing propulsion technologies for future space access vehicles--it discusses the flow starting process in supersonic and hypersonic air-inlets. A study is conducted, with the aid of numerical simulations, based on an inviscid model of a thermally perfect gas. Effects of boundary-imposed temporal and spatial gradients on the inlet starting phenomenon are documented for the first time. It is shown that purely accelerative starting is generally not possible, for inlets of any positive contraction, unless thousands of g 's of acceleration are imposed. It is proposed that removal of frangible structures, such as fast rupturing diaphragms, be used to impose sufficiently high spatial gradients, as necessary to permit starting beyond Kantrowitz' limit. It is shown that, for a perforated diffuser, starting takes place if a sonic line, at the leading edge of a slit, occurs at an area ratio equal to, or higher than, that corresponding to Kantrowitz' limit.

The propagation of ionizing cylindrical magnetogasdynamic shock wave in rotational axisymmetric self-gravitating perfect gas under isothermal flow condition is investigated. Mathematical model for the considered problem using system of PDEs is presented. The density, magnetic pressure, azimuthal fluid velocity and axial fluid velocity are assumed to be varying according to power law with distance from the axis of symmetry in the undisturbed medium. The flow variables are expanded in power series and using that the zeroth and first order approximations are discussed. Solutions for zeroth order approximation are constructed in approximate analytical form. The effect of flow parameters namely: gravitational parameter $$G_{0}$$ , shock Cowling number $$C_{0}$$ , rotational parameter L and ambient density variation index q are studied on the flow variables and total energy of disturbance. Distribution of gasdynamical quantities are discussed. Radial fluid velocity and mass tends to zero near the axis of symmetry in general; but magnetic pressure, axial fluid velocity, non-dimensional components of vorticity vector $$l_{\theta }^{(0)}$$ and $$l_{z}^{(0)}$$ tend to positive infinity near the axis of symmetry. Azimuthal fluid velocity decreases as we move inwards from the shock to the axis of symmetry. Density and pressure vanish near the axis of symmetry thus forming a vacuum there. $$J_{0}$$ decreases with increase in value of ambient density variation index q or gravitational parameter $$G_{0}$$ ; whereas it increases with increase in value of rotational parameter L or shock Cowling number $$C_{0}$$ .

The oscillating-water-column (OWC) wave energy converter with air turbine has been object of extensive research and development effort, including the deployment of floating and fixed-structure full-sized prototypes into the sea. It consists of a hollow (fixed or floating) structure, open to the sea below the water surface. Wave action alternately compresses and decompresses the air trapped above the inner water free-surface in a chamber, which forces air to flow through a turbine coupled to an electrical generator. The spring-like effect of air compressibility in the chamber is related to the density-pressure relationship. It is known to significantly affect the power performance of the full-sized converter, and is rarely accounted for in theoretical modelling, and even more rarely in physical model testing at reduced scale, as appears from the literature review. Three theoretical models of increasing complexity are analysed and compared: (i) the incompressible air model; (ii) the isentropic process model; (iii) and the (more difficult and rarely adopted) adiabatic non-isentropic process model in which losses due to the imperfectly efficient turbine are accounted for. The air is assumed as a perfect gas. The hydrodynamic modelling of wave energy absorption is based on linear water wave theory. The validity of the various simplifying assumptions, especially in the aero-thermodynamic domain, is illustrated by a case study with numerical results for a fixed-structure OWC equipped with a Wells turbine. Results are shown for regular and irregular waves, and for a theoretical simulation of model testing in wave tank at small scale.

The non-similarity solution for the propagation of a strong cylindrical shock wave in a self-gravitating and rotational axisymmetric dusty gas, having variable azimuthal and axial fluid velocities is obtained. The dusty gas is assumed to be a mixture of small solid particles of micro size and perfect gas. The equilibrium flow conditions are assumed to be maintained. The density of the mixture and the fluid velocities in the ambient medium are assumed to be varying and obeying an exponential law. The shock wave moves with variable velocity and the total energy of the wave is non-constant. The effects of variation of the mass concentration of solid particles in the mixture, the ratio of the density of solid particles to the initial density of the gas, and the gravitational parameter on the flow variables in the region behind the shock are investigated at a given time in both the rotating and non-rotating cases. Our analysis reveals that an increase in gravitational parameter or in the ratio of the density of solid particles to the initial density of the gas surprisingly the shock strength increases and remarkable differences are found in the distribution of flow variables in both the rotating and non-rotating cases. An increase in time also, increases the shock strength in the case of isothermal flow, but to decrease the shock strength in the case of adiabatic flow in general. Further, it is investigated that the consideration of isothermal flow increases the shock strength. A comparison is made between the solutions in isothermal and adiabatic flow cases with or without gravitational effects in both the rotating and non-rotating medium. The obtained solutions are applicable for arbitrary values of time.

The ellipsoidal statistical (ES) model of the Boltzmann equation for a polyatomic gas with constant specific heats (calorically perfect gas), proposed by Andries et al. (Eur J Mech B Fluids 19:813, 2000), is extended to a polyatomic gas with temperature-dependent specific heats (thermally perfect gas). Then, the new model equation is applied to investigate the structure of a plane shock wave with special interest in $$\hbox {CO}_2$$ gas, which is known to have a very large bulk viscosity, and in the case of relatively strong shock waves. A numerical analysis, as well as an asymptotic analysis for large bulk viscosity, is performed in parallel to the previous paper by two of the present authors (Kosuge and Aoki, in: Phys Rev Fluids 3:023401, 2018), where the structure of a shock wave in $$\hbox {CO}_2$$ gas was investigated using the ES model for a polyatomic gas with constant specific heats. From the numerical and analytical results, the effect of temperature-dependent specific heats on the structure of a shock wave is clarified.

This review will focus on perfect gas models developed to predict the performances of counterflow vortex tubes. It includes empirical and thermodynamics models, models of heat exchangers, models based on a pressure gradient, models based on the momentum transfer with particles spinning inward and models based on unsteady phenomena like the vortex breakdown. A detailed comparison of these models shows that most of them solve the same set of equations but lead to different explanations regarding the flow and heat transfer phenomena within Ranque-Hilsch tubes. The energy balance links the hot and cold flow temperatures for a given cold mass fraction as long as kinetic energy is included in the analysis. Secondly, almost all models consider the radial momentum balance, which reduces to a simple expression linking the pressure gradient and the tangential velocity. Usually, a given velocity profile (forced vortex or Rankine vortex) closes this set of equations. The form of the velocity profile may be dependent on the magnitude of the radial flow. None of the analytical models analyzed in this paper could predict all the geometrical parameters of a vortex tube. Empirical knowledge is still required. However, the pressure difference between the inlet and the cold outlet is a major component. It is related to the pressure drop of the cold air downstream of the vortex tube. To predict the main vortex tube dimensions (diameter and length), the most promising avenue is linked to the occurrence and the good localization of the vortex breakdown inside the tube. This review ends with some future views to improve the predictions of the existing models and the knowledge of the temperature separation phenomenon within vortex tubes.

Shock-wave–boundary-layer interaction is one of the most important phenomena in hypersonic flights due to its ubiquitous presence and its extreme effects on the aerothermodynamic loads on the aircr...

The aim of this work is to develop a calculation model based on the method of characteristics making it possible to study the effect of the stagnation pressure of the combustion chamber on the 2D and axisymmetric minimum length nozzle design giving a uniform and parallel flow at the exit section. The model is based on the use of the real gas approach. The co-volume and the intermolecular interaction effect are taken into account by the use of the Berthelot state equation. The effect of molecular vibration is considered in our model to evaluate the behaviour of gas at a high temperature. In this case, the stagnation pressure and the stagnation temperature are important parameters in our model. The resolution of the algebraic equations is done by the finite difference corrector predictor algorithm. The validation of the results is controlled by the convergence of the critical section ratios calculated numerically as obtained by the theory. The mass and the thrust are evaluated to improve the efficiency of the nozzle. The comparison is made with the high temperature and perfect gas models. The application is made for air.

In this paper, we study the vibration excitation on the reflection of shock waves in hypersonic flows by using analytical and computational approaches. First, a theoretical approach is established to solve the shock relations which are further applied to develop the shock polar analytical method for high-temperature air. Then, a comparative investigation using calorically perfect gas model and thermally perfect gas model considering vibration excitation indicates an obvious change to the overall profile of the shock polar. The post-shock pressure increases within the strong branch of the shock polar while decreases within the weak branch due to vibration excitation of air molecules. A more notable phenomenon is the increase in the maximum deflection angle of the shock polar which can significantly influence the detachment criterion of shock reflection transition in high-temperature air flows. The shock polar analysis of shock reflection shows that the vibration excitation result in an obvious increase to the detachment criterion while a slight increase to the von Neumann criterion. A series of computations are conducted to confirm the above analytical findings on the shock reflection considering the vibration excitation. A slight difference of transition criterion between the theory and computations is found to be caused by the existence of the expansion fan which is an inherent flow structure. The proposed shock polar analytical method is proved to be an effective but simple approach for the study of shock wave reflections in hypersonic flows.

The energy capabilities of acceleration devices are theoretically analyzed, including various ramjet-in-tube options for gas-dynamic acceleration of massive (1 to 40 kg) projectiles under ground conditions up to velocities of 2–3 km/s. Simple quasi-one-dimensional models for a perfect gas are used in the computations. It is demonstrated that the use of a ramjet-in-tube accelerator with a closed exit allows the velocities of acceleration of massive projectiles to be increased to 3 km/s, which is twice greater than the values that can be obtained with available gunpowder-based methods.

The development of inviscid and viscous two-dimensional subsonic disturbances in the supersonic flat-plate boundary layer of a vibrationally excited gas is investigated on the basis of the linear stability theory. The system of two-temperature gas dynamics which includes the Landau-Teller relaxation equation is used as the initial model. Undisturbed flow is described by the self-similar boundary-layer solution for a perfect gas. It is shown that in the inviscid approximation excitation decreases the maximum growth rate of the most unstable second mode by 10–12% as compared with an ideal gas. The neutral stability curves are calculated for the first and second most unstable modes at the Mach numbers M = 2.2, 4.5, and 4.8. For both modes the critical Reynolds numbers at maximum excitation are greater by 12–13% than the corresponding values for the perfect gas.

The effects of air dissociation on flat-plate hypersonic boundary-layer flow instability and transition prediction are studied. The air dissociation reactions are assumed to be in the chemical equilibrium. Based on the flat-plate boundary layer, the flow stability is analyzed for the Mach numbers from 8 to 15. The results reveal that the consideration of air dissociation leads to a decrease in the unstable region of the first-mode wave and an increase in the maximum growth rate of the second mode. High frequencies appear earlier in the third mode than in the perfect gas model, and the unstable region moves to a lower frequency region. When the Mach number increases, the second-mode wave dominates the transition process, and the third-mode wave has little effect on the transition. Moreover, when the Mach number increases from 8 to 12, the N-factor envelope becomes higher, and the transition is promoted. However, when the Mach number exceeds 12, the N-factor envelope becomes lower, and the transition is delayed. The N-factor envelope decreases gradually with the increase in the altitude or Mach number.

The triple configurations of stationary shock waves with negative slope angle of the reflected shock to the velocity vector of the supersonic stream in front of the triple point (“inverse” triple configurations) are considered. “Inverse” configurations with the maximum relations of flow parameters at the tangential discontinuity after the triple point are determined. Extreme relations of the flow parameters downstream the “inverse” configurations are compared with the analogous extreme parameters attained on the whole set of the triple-shock configurations that appear in supersonic streams of the inviscid perfect gas.

形態: カラー図版あり, Physical characteristics: Original contains color illustrations, Accepted: 2018-10-01, 資料番号: PA1910019000

A new framework, Eigen Analysis in General Curvilinear Coordinates (EAGCC), is presented for internal propagation of linear acoustic flow disturbances through irregular but smoothly varying duct geometries and non-uniform but smoothly varying mean flows. The framework is based on an eigen analysis of the linearised Euler equations for a perfect gas formulated in a general curvilinear coordinate system. A series of test cases are studied, from a simple uniform cylindrical annular duct with uniform mean flow to an axially and circumferentially non-uniform duct with non-uniform mean flow, which together validate the method for acoustic propagation through non-uniform annular ducts and non-uniform but irrotational and homentropic mean flow: although the framework provides for rotational and non-homentropic mean flow, and for modelling vortical and entropic flow perturbations, these features are not validated in this paper. Two propagation methods are presented. The first is a one-way “single sweep” calculation, in which only information travelling in the direction of propagation is retained. The second is an iterative “two-way sweep” method that accurately captures reflected waves and returns transmitted and reflected perturbations. Previous eigenvector analyses were subject to limitations on geometry and mean flow (for instance slowly-varying ducts) that are not required in the current method, for which the only limitations are that the duct and mean flow vary smoothly with position. This work extends the scope of the eigenvector approach to include acoustic problems previously limited to volumetric or surface-based methods.

The presented results of computations of the aerodynamic and acoustic characteristics of an isolated symmetric NACA0012 airfoil with a blunt trailing edge in a subsonic homogeneous viscous perfect gas flow at zero angle of attack are obtained using the MP5 modified finite-difference scheme proposed in this study. The computations are accomplished within the zonal RANS–IDDES approach engaging the basic RANS Spalart–Allmaras model. A synthetic turbulence generator with a three-dimensional source is used to create turbulent content at the entrance to the IDDES domain. A series of model problems are considered, whose solutions allowed tuning the parameters of the proposed difference scheme and solving some methodological problems related to processing the simulation results.

The aim of this paper is to numerically analyze the energy separation phenomenon in turbulent compressible swirling flow in a cylindrical tube. In that sense, the energy separation in a vortex tube with orifice at cold end closed completely is examined numerically using OpenFOAM software. Obtained results are validated with the experimental ones. For numerical calculations, both two-equation (standard k-ε) and full Reynolds stress turbulence models (LRR) are used. The computational domain is considered to be two-dimensional, and the working fluid - air is treated as calorically perfect gas. Mesh independence test is carried out for four different mesh sizes. Distributions of swirling flow intensity, average swirl and angular velocity clearly show the influence of the swirl presence in the flow. The values of these quantities point to the physics of this extremely complex flow-thermodynamic phenomenon, such is the energy separation. Based on values and distributions of these flow quantities a comparison between incompressible and compressible turbulent swirling flow is performed.

We consider acoustic propagation in a particle-laden fluid, specifically, a perfect gas, under a model system based on the theories of Marble (1970) and Thompson (1972). Our primary aim is to understand, via analytical methods, the impact of the particle phase on the acoustic velocity field. Working under the finite-amplitude approximation, we investigate singular surface and traveling wave phenomena, as admitted by both phases of the flow. We show, among other things, that the particle velocity field admits a singular surface one order higher than that of the gas phase, that the particle-to-gas density ratio plays a number of critical roles, and that traveling wave solutions are only possible for sufficiently small values of the Mach number.

To study the Reynolds stress budgets, direct numerical simulations of high-temperature supersonic turbulent channel flow for thermally perfect gas and calorically perfect gas are conducted at Mach number 3.0 and Reynolds number 4800 combined with a dimensional wall temperature of 596.30 K. The reliability of the direct numerical simulation data is verified by comparison with previous results ( J Fluid Mech 1995, vol. 305, pp.159–183). The effects of variable specific heat are important because the vibrational energy excited degree exceeds 0.1. The viscous diffusion, pressure–velocity gradient correlation, and dissipation terms in the Reynolds stress budgets for TPG, except the streamwise component, are larger than those for calorically perfect gas close to the wall. Compressibility-related term decreases when thermally perfect gas is considered. The major difference for both gas models is mainly due to variations in mean flow properties. Inter-component transfer related to pressure–velocity gradient correlation term can be distinguished into inner and outer regions, whose critical position is approximately 16 for both gas models.

The noise of jet and rocket engines involves the coupling of sound to swirling flows and to heat exchanges leading in the more complex cases of triple interactions to acoustic-vortical-entropy (AVE) waves. The present paper presents the derivation of the AVE equation for axisymmetric linear non-dissipative, compressible perturbations of a non-homentropic, swirling mean flow, with constant axial velocity and constant angular velocity for a perfect gas with constant density. The axisymmetric AVE wave equation is obtained for the radial velocity perturbation, specifying its radial dependence for any frequency and axial wavenumber. The AVE wave equation in the case of zero axial wavenumber, corresponding to cylindrical AVE waves, has no singularities for finite radius, including the sonic radius, where the isothermal Mach number for the swirl velocity is unity. The exact solution of the AVE wave equation for the fundamental axisymmetric mode with zero axial wavenumber is obtained without any restriction on frequency, as series expansions of Gaussian hypergeometric type: (i) covering the whole flow region; (ii) specifying the wave field at the sonic radius; (iii) specifying near-axis and asymptotic scaling for small and large radius. Using polarization relations among wave variables specifies exactly and allows the plotting of the perturbations of: (i,ii) the radial and azimuthal velocity; (iii,iv) pressure and mass density; (v,vi) entropy and temperature. Thus the extension of cylindrical acoustic waves, that are specified by Bessel functions, to cylindrical acoustic-vortical-entropy waves, is specified by Gaussian hypergeometric functions.

The propagation of diverging cylindrical shock waves in a weakly conducting dusty gas (mixture of a perfect gas and small solid particles) under the influence of a spatially variable axial magnetic induction, is investigated. The initial density of the medium obeys a power law. The total energy of the flow-field behind the shock is not constant, but assumed to be increasing due to time dependent energy input. The effects of variation of initial density, the mass concentration of solid particles (kp), the ratio of the density of the solid particles to the density of the perfect gas in the undisturbed mixture (G0), and the presence of magnetic induction, on the propagation of the shock and the flow-field behind it are investigated. Keywords: Shock wave, Self-similar flow, Variable initial density, Variable initial magnetic induction, Variable energy input, Weakly conducting dusty gas

In this study, a less-dissipative hybrid AUSMD scheme considering the linearized approximated solution around the material interfaces of compressible multi-component flows is proposed. A high-resolution reconstruction scheme, so-called MUSCL + THINC, has been devised by combining the MUSCL method with the Tangent of Hyperbola for Interface Capturing technique (THINC) under the boundary variation diminishing concept, which is used to determine the cell-interface values to evaluate the AUSMD flux. Several perfect gas and multi-component flow problems are selected as the benchmark test cases. The flow models we use here are the perfect gas Euler equations and the multi-phase five-equation flow model. We compared the proposed MUSCL + THINC-type AUSMD scheme with the original MUSCL-type AUSMD scheme to verify its capability of capturing shock waves, expansion fans, and material interfaces, which are identified as a well-defined sharp jump in volume fraction. Numerical results of all benchmark tests show that the MUSCL + THINC-type AUSMD solver is superior to the original MUSCL-type AUSMD in resolving shock waves, expansion fans, and interfaces. In particular, the solution quality for expansion fans and interfaces on coarse grids is greatly improved by the MUSCL + THINC-type AUSMD scheme.

The ideal gas model with temperature-independent heat capacities is the most widely used thermodynamic model in gas turbine cycle simulations. This model is sometimes known as the “perfect gas model”. Closed analytical expressions for specific works and temperatures of the cycle are obtained in this way. If the results are accurate enough then the perfect gas model becomes a powerful analysis tool because its simplicity. For this reason it is the usually chosen option when energy, exergy or thermoeconomic assessments and optimizations of gas turbine cycles are carried out. However, there is a shortage of research works about the analysis of the uncertainty in the calculation of the performance parameters of open-cycle gas turbines with respect to the ideal gas model-based approach (ideal gas with temperature-dependent heat capacities). This analysis is presented in this paper for the simple cycle taking the net specific work output or specific power of the cycle and its Specific Fuel Consumption (SFC) as the performance parameters to be analyzed. First, to gain in internal coherence, an accurate thermodynamic model of the simple cycle based on the ideal gas assumption with temperature-dependent heat capacities is presented. For the sake of accuracy the isobaric heat capacity functions used in this model for every gaseous component present in the cycle are the employed in developing its actual multiparameter equations of state as real fluids. Once this model is established the perfect gas simplification is applied which requires a procedure or rule to evaluate the constant heat capacity values needed. In many cases this rule is not always given or is not clearly specified in the specific literature. In this paper four different evaluation methods (named as A, B, C and D) are considered. These methods are designed to be directly run from known input fixed parameters of the cycle model. The analysis of the absolute and relative errors in computations with the perfect gas approach with the four heat capacity evaluation methods is then carried out. The main result from the analysis is that the own configuration of the open-cycle can lead to an increase (amplification) of the uncertainty in the values of the performance parameters. It is also observed that: (1) this amplification also depends on the method used to evaluate the heat capacities and (2) for a given evaluation method the amplification of the deviations may affect the performance parameters differently. As an example, maximum relative errors of 4.4% and −19.2% are observed in the net specific work output with methods C and D respectively for compressor pressure ratios from 5:1 to 40:1 and turbine inlet temperatures from 1200 K to 1800 K. For the SFC maximum values are −19.51% with method C and 3.95% with method D.

Direct numerical simulations of temporally evolving supersonic turbulent channel flow of thermally perfect gas are conducted at Mach number 3.0 and Reynolds number 4800, combined with constant dime...

The isosteric heat of adsorption strongly associates with the energetics of the adsorption processes. Being a direct function of the uptake amount, accurate modelling of the isosteric heat of adsorption is crucial in the design and development of adsorption systems. The isosteric heat of adsorption is often calculated using the Clausius-Clayperon equation with the perfect gas assumption and negligible adsorbed phase volume. We present a thermodynamic model of the isosteric heat of adsorption that addresses the non-ideal behaviour and the variation in the adsorbed phase density. The model is first validated using experimental data in comparison with the available models in the literature that invoke the ideal gas assumption with negligible adsorbed phase volume. Using these models, the isosteric heat for adsorption processes is examined from partial vacuum to high pressure as well as adsorption temperatures above the critical point. The impact of the prediction by each model on the system performance is then assessed in terms of the theoretical COP. For the realistic evaluation of system COP, an improved equilibrium cycle model is developed and the system performance is investigated using various models for the isosteric heat of adsorption. For adsorption at partial vacuum conditions, the COP values predicted by the ideal model are up to 1.8% higher when compared to the calculations using the present model. For high-pressure adsorption below the critical temperature, for example, Maxsorb III + R134a pair, the present model predicts 13% lower COP than the models available in the literature. The variation in the adsorbed phase density addressed in the present model leads to a higher value of isosteric heat (3.8%–8.6%) for adsorption above the critical temperature.

This paper describes a novel hypersonic facility to reproduce the high stagnation pressures and temperatures necessary for the accurate simulation of hypersonic flows in the range Mach 5–7, while p...

It is known from the literature that Large Eddy Simulations of dense gas flows can prove very useful in order to better understand the behavior of friction losses in Organic Rankine Cycle turbines and expanders. Yet, no dedicated turbulence closure models exist for such flows. In this study, the authors lay the fondations for the development of turbulence closure models in dense gas flows. The Subgrid-Scale terms are first rigorously derived from the filtered Navier-Stokes equations. Additional terms to the well-known Subgrid-Scale closure terms are identified in the dense gas context. Using Direct Numerical Simulation, the variances of Subgrid-Scale terms in the filtered momentum equations are computed both for the dense and perfect gas cases and significant differences are revealed between the two cases. A model using only filtered fields as input is derived for one of the dense gas specific Subgrid-Scale terms using a Correlation Patterns Modeling approach. Preliminary a priori tests indicate that this approach can be easily implemented and provides promising results.

For a successful space programme, the reusable spacecraft should survive numerous re-entry conditions. The re-entry of almost all the reusable space shuttles resembles a flat plate at high angles of attack because of its flat windward surface. The feasibility of concave ventral surface in space shuttles is analysed computationally with a commercially available solver scFLOW. A full three-dimensional Navier–Stokes equations are solved over a thin concave plate at different angles of attack to a hypersonic flow. The peak temperature and drag coefficients of different eccentric plates are compared with that of a flat plate normal to the flow. The air is assumed to be thermally perfect gas. The flow is assumed to be continuum. The total heat transfer rates and peak heat fluxes of a concave plate are compared with the flat plate. This paper discusses the results of these simulations and how the concavity behaves in the re-entry of spacecraft.

This chapter gives the general laws of the transport and their features in gases: physical kinetics, transport phenomenology, transport in perfect gases, transport in perfect gas mixtures, and pressure effect on transport in gases, Knudsen field transport, pure real gases at moderate pressures, transport in pure gases at high pressure, and gives seven worked examples.

The performance of a rotatable Pitot cylinder probe was experimentally investigated in the calibration test section of a closed loop organic vapor wind tunnel with the working fluid Novec™ 649 at elevated density level. Subsonic up to high subsonic flow conditions (M = 0.5 – 0.7) were covered by the experiments. The data reduction process for obtaining Mach numbers and velocity based on non-ideal flow calculations and corresponding isentropic relations were reviewed. The theoretical results were compared with experimental data. It was found that in the case of high subsonic non-ideal gas flows, significant deviations in comparison with conventional perfect gas flows occurred.

Flowfields of various gasodynamic parameters at high supersonic flows about the air intakes of flying vehicles are analyzed. Mathematical model of high supersonic flows is set and verified. Numerical simulation of perfect gas flow in non-profiled ducts of air intakes is provided. Various methods of multicomponent mixture simulation are used. Influence of flow multi-componence of shock waves near the head of flying vehicle is considered.

In the earlier chapters, we studied the gas dynamics of a perfect gas. In this chapter, we will study the dynamics of the flow of steam through nozzles. Historically, the theory of the flow of steam through nozzles was developed first in the late 1800 and early 1900 s.