An Assessment of Shock-Disturbances Interaction Considering Real Gas Effects

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
K. Hejranfar ◽  
S. Rahmani
Keyword(s):  
Theoretical Analysis ◽  
The Body ◽  
Mathematical Function ◽  
Perfect Gas ◽  
Real Gas ◽  
One Dimensional ◽  
Wide Range ◽  
Different Types ◽  
Real Gas Effects ◽  
Analytical Relations

In this study, a theoretical analysis is performed to assess the interaction of freestream disturbances with a plane normal shock considering real gas effects. Such effects are important in a field with high velocities and high temperatures. To perform the theoretical analysis, the downstream disturbances field is expressed as a mathematical function of the upstream one by incorporating real gas effects in the formulation. Here, the linearized one-dimensional perturbed unsteady Euler equations are used for the classification of the downstream/upstream disturbances field and the linearized one-dimensional perturbed Rankine–Hugoniot equations are applied to provide a relationship between the disturbances field of two sides of the shock. To incorporate real gas effects in the formulation, real gas relations and equilibrium air curve-fits are used in the resulting system of equations. The general formulation presented here may be simplified to derive Morkovin's formulation by the perfect gas assumption. The magnitudes of downstream disturbances field resulting from different types of upstream disturbances field (entropy wave and fast/slow acoustic waves) with the shock are expressed by appropriate analytical relations. Results for different disturbance variables are presented for a wide range of upstream Mach number considering real gas effects and compared with those of the perfect gas and some conclusions are made. The effects of the presence of body are also studied theoretically and the analytical relations for the magnitude of the pressure disturbance at the body for different types of upstream disturbances field considering real gas effects are provided and their results are presented and discussed.

scholarly journals TORTURE INJURIES

2011 ◽  
Vol 18 (02) ◽  
pp. 285-288
Author(s):  
KHURRAM SOHAIL RAJA ◽  
HUMAIRA ARSHAD ◽  
FARIDA MANZUR
Keyword(s):  
Blunt Trauma ◽  
The Body ◽  
Physical Trauma ◽  
Medical Board ◽  
Wide Range ◽  
Different Types ◽  
Psychological Element ◽  
Trauma Victims ◽  
Study Setting

Objective: To examine the different type of injuries after police torture. Design: Torture study. Setting: Office of District Standing Medical Board, in DHQ Hospital Faisalabad. Period: From 1.1.2009 to 31.12.2009. Material & Methods: A study of 300 victims of alleged police torture examined by the District Standing Medical Board (DSMB) Faisalabad. Most of the victims at the time of examination were showing visible evidence of Physical trauma. Victims were males. Examination was conducted on the directions of judicial magistrates and District & Session Judge Faisalabad. Conclusion: A wide range of different types of injuries was observed on various parts of the body. Blunt trauma was most frequent. Psychological element of torture was also seen in some victims.

Performance and optimization of gas turbines with real gas effects

2001 ◽  
Vol 215 (4) ◽  
pp. 507-512 ◽  
Author(s):  
A Guha
Keyword(s):  
Gas Turbines ◽  
Pressure Ratio ◽  
Gas Analysis ◽  
Perfect Gas ◽  
Explicit Equation ◽  
Optimum Pressure ◽  
Real Gas ◽  
Turbine Performance ◽  
Real Gas Effects ◽  
Optimum Relation

The influence of various levels of mathematical modelling on gas turbine performance is systematically analysed. It is shown that internal combustion with real gas effects gives rise to an optimum turbine entry temperature which does not arise in a perfect gas analysis and has not been described previously in the literature. At any pressure ratio, the maximum possible efficiency with real gas effects is significantly lower (15-20 per cent) than the maximum possible value predicted by a perfect gas analysis. An explicit equation has been derived for determining the optimum pressure ratio as a function of turbine entry temperature and component efficiencies. It is shown that the optimum design depends very strongly on turbine and compressor efficiencies. It is demonstrated that the optimum relation between pressure ratio and turbine entry temperature depends strongly on whether the optimization is carried out at fixed pressure ratios or at fixed temperatures. All previous references seem to have considered only the latter method.

scholarly journals Compressible flow at high pressure with linear equation of state

2018 ◽  
Vol 843 ◽  
pp. 244-292 ◽  
Author(s):  
William A. Sirignano
Keyword(s):  
Equation Of State ◽  
Compressible Flow ◽  
Sound Speed ◽  
Ideal Gas ◽  
Real Gas ◽  
Cubic Equation Of State ◽  
Cubic Equation ◽  
Wide Range ◽  
Real Gas Effects ◽  
Flow Configurations

Compressible flow varies from ideal-gas behaviour at high pressures where molecular interactions become important. It is widely accepted that density is well described through a cubic equation of state while enthalpy and sound speed are functions of both temperature and pressure, based on two parameters, $A$ and $B$, related to intermolecular attraction and repulsion, respectively. Assuming small variations from ideal-gas behaviour, a closed-form approximate solution is obtained that is valid over a wide range of conditions. An expansion in these molecular interaction parameters simplifies relations for flow variables, elucidating the role of molecular repulsion and attraction in variations from ideal-gas behaviour. Real-gas modifications in density, enthalpy and sound speed for a given pressure and temperature lead to variations in many basic compressible-flow configurations. Sometimes, the variations can be substantial in quantitative or qualitative terms. The new approach is applied to choked-nozzle flow, isentropic flow, nonlinear wave propagation and flow across a shock wave, all for a real gas. Modifications are obtained for allowable mass flow through a choked nozzle, nozzle thrust, sonic wave speed, Riemann invariants, Prandtl’s shock relation and the Rankine–Hugoniot relations. Forced acoustic oscillations can show substantial augmentation of pressure amplitudes when real-gas effects are taken into account. Shocks at higher temperatures and pressures can have larger pressure jumps with real-gas effects. Weak shocks decay to zero strength at sonic speed. The proposed framework can rely on any cubic equation of state and can be applied to multicomponent flows or to more complex flow configurations.

Mathematical aspects of the theory of inviscid hypersonic flow

1991 ◽  
Vol 335 (1637) ◽  
pp. 121-138 ◽  
Keyword(s):  
Chemical Reactions ◽  
Mathematical Analysis ◽  
Solution Structure ◽  
Well Posedness ◽  
Two Dimensional ◽  
Open Problems ◽  
Real Gas ◽  
One Dimensional ◽  
Two Dimensional Flow ◽  
Real Gas Effects

This paper reviews some differential equations arising in the theory of inviscid hypersonic gasdynamics. The only real-gas effects that we have incorporated are simple models for chemical reactions. After describing what is known about the solution structure of these equations in unsteady one-dimensional and steady two- dimensional flow, we make some conjectures about the well-posedness and regularization of certain specific open problems which have not yet been susceptible to mathematical analysis.

The interaction of a shock wave with a laminar boundary layer at a compression corner in high-enthalpy flows including real gas effects

1997 ◽  
Vol 342 ◽  
pp. 1-35 ◽  
Author(s):  
S. G. MALLINSON ◽  
S. L. GAI ◽  
N. R. MUDFORD
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Shock Wave ◽  
Gas Flows ◽  
Perfect Gas ◽  
Experimental Conditions ◽  
Real Gas ◽  
High Enthalpy ◽  
Compression Corner ◽  
Real Gas Effects

The high-enthalpy, hypersonic flow over a compression corner has been examined experimentally and theoretically. Surface static pressure and heat transfer distributions, along with some flow visualization data, were obtained in a free-piston shock tunnel operating at enthalpies ranging from 3 MJ kg−1 to 19 MJ kg−1, with the Mach number varying from 7.5 to 9.0 and the Reynolds number based on upstream fetch from 2.7×104 to 2.7×105. The flow was laminar throughout. The experimental data compared well with theories valid for perfect gas flow and with other relevant low-to-moderate enthalpy data, suggesting that for the current experimental conditions, the real gas effects on shock wave/boundary layer interaction are negligible. The flat-plate similarity theory has been extended to include equilibrium real gas effects. While this theory is not applicable to the current experimental conditions, it has been employed here to determine the potential maximum effect of real gas behaviour. For the flat plate, only small differences between perfect gas and equilibrium gas flows are predicted, consistent with experimental observations. For the compression corner, a more rapid rise to the maximum pressure and heat transfer on the ramp face is predicted in the real gas flows, with the pressure lying slightly below, and the heat transfer slightly above, the perfect gas prediction. The increase in peak heat transfer is attributed to the reduction in boundary layer displacement thickness due to real gas effects.

Calculations of Real-Gas Effects in Flow Through Critical-Flow Nozzles

1964 ◽  
Vol 86 (3) ◽  
pp. 519-525 ◽  
Author(s):  
Robert C. Johnson
Keyword(s):  
Mass Flow ◽  
Room Temperature ◽  
The Other ◽  
Critical Flow ◽  
Real Gas ◽  
One Dimensional ◽  
Real Gas Effects ◽  
Computer Calculations ◽  
Flow Through

Computer calculations have been made of how real-gas effects modify the conventional one-dimensional equations for mass flow of air, nitrogen, oxygen, hydrogen, argon, helium, and steam through a nozzle. The results indicate that for critical flow of air, at room temperature and 100 atmospheres pressure, real-gas effects of 3 1/2 percent exist. Similar magnitudes are found for the other gases.

On the interaction of internal waves and surface gravity waves

1974 ◽  
Vol 63 (4) ◽  
pp. 773-800 ◽  
Author(s):  
John E. Lewis ◽  
Bruce M. Lake ◽  
Denny R. S. Ko
Keyword(s):  
Surface Wave ◽  
Theoretical Analysis ◽  
Internal Wave ◽  
Internal Waves ◽  
Gravity Waves ◽  
Surface Gravity ◽  
One Dimensional ◽  
Surface Gravity Waves ◽  
Wide Range ◽  
The One

The perturbation of pre-existing surface gravity waves caused by the presence of an internal wave was studied both experimentally and analytically. An extensive series of experiments was performed, and quantitative results were obtained for the one-dimensional monochromatic interaction of internal waves and surface gravity waves. Internal wave-induced surface slope, amplitude and wavenumber modulations were measured for a wide range of interaction conditions. A complementary theoretical analysis, based on the conservation approach of Whitham (1962) and Longuet-Higgins & Stewart (1960,1961), was performed and a closed form solution obtained for the one-dimensional wave interaction. Both the theory and the experiment demonstrate that the effect increases with interaction distance. The maximum interaction effect is found to occur when the phase speed of the internal wave and the group velocity of the surface wave are matched. The phase of the internal wave at which maximum surface-wave modulation occurs is found to be a sensitive and continuous function of the relative wave speeds. The experimental data are in good agreement with the present theoretical analysis.

scholarly journals Novel Implementation of Audio Encryption Using Pseudorandom Byte Generator

2021 ◽  
Vol 11 (21) ◽  
pp. 10190
Author(s):  
Borislav Stoyanov ◽  
Tsvetelina Ivanova
Keyword(s):  
Theoretical Analysis ◽  
Chaos Theory ◽  
Signal To Noise Ratio ◽  
Mathematical Function ◽  
Signal To Noise ◽  
Change Rate ◽  
Different Types ◽  
Audio Encryption ◽  
Noise Ratio ◽  
Audio Files

In this paper, we present an algorithm for encrypting audio files based on the Ikeda map, a mathematical function of chaos theory. Detailed experimental, security and theoretical analysis is provided on the proposed algorithm using histogram analysis, using different measurements including the signal-to-noise ratio, the peak signal-to-noise ratio, the number of samples change rate and the correlation coefficient. The provided results show a highly secure and strong algorithm against different types of attacks.

Discharge Coefficients of Critical Venturi Nozzles for CO2 and SF6

2000 ◽  
Vol 122 (4) ◽  
pp. 730-734 ◽  
Author(s):  
Shin-ichi Nakao ◽  
Masaki Takamoto
Keyword(s):  
Boundary Layer ◽  
Large Deviation ◽  
Nonequilibrium Flow ◽  
Theoretical Estimation ◽  
Perfect Gas ◽  
Number Range ◽  
Real Gas ◽  
Discharge Coefficients ◽  
Isentropic Flow ◽  
Real Gas Effects

The discharge coefficients of critical Venturi nozzles were measured for CO2 and SF6 on the Reynolds number range from 3×103 to 2×105. The results showed that the measured discharge coefficients for both gases were about 2 percent larger than the theoretical estimation based on the assumption of isentropic flow of a perfect gas and this large deviation could not be reduced even by introducing real gas effects. The experimental results also showed that the large deviation for CO2 could be explained through the assumption of a nonequilibrium flow at the throat. On the other hand, the reason of the deviation observed for SF6 has not been clear yet, but one possible explanation would be the inadequate estimation of the boundary layer at the throat because the theory is based on the laminar boundary layer of a perfect gas. [S0098-2202(00)02004-6]

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