Speed of Sound and Mach Number

2020 ◽  
pp. 123-136
Author(s):  
Rose G. Davies
Keyword(s):  
Mach Number ◽  
Speed Of Sound

A Theory for the High-Speed Flow of Gas-Solids Mixtures under Conditions of Equilibrium and Constant Fractional Lag

1969 ◽  
Vol 184 (3) ◽  
pp. 59-66 ◽  
Author(s):  
B. N. Cole ◽  
H. M. Bowers ◽  
F. R. Mobbs
Keyword(s):  
Mach Number ◽  
Speed Of Sound ◽  
Gas Dynamics ◽  
High Speed ◽  
Solid Particles ◽  
High Speed Flow ◽  
One Dimensional ◽  
Dimensional Flow ◽  
Speed Flow ◽  
Constant Area

A theory is presented for the high-speed, one-dimensional flow of a gas-solids mixture, assuming constant fractional lags of temperature and velocity between the solid particles and the gas. A mixture speed of sound is is derived and used as the basis of a mixture Mach number. Expressions are deduced which are parallel to many well-known relationships in orthodox one-dimensional gas dynamics. The investigation covers frictionless flow in a variable area duct and flow with friction in a constant area duct. The effect of solids volume is also taken into account.

On the breakdown of characteristics solutions in flows with vibrational relaxation

1967 ◽  
Vol 27 (1) ◽  
pp. 49-57 ◽  
Author(s):  
B. S. H. Rarity
Keyword(s):  
Relaxation Time ◽  
Mach Number ◽  
Supersonic Flow ◽  
Steady Flow ◽  
Speed Of Sound ◽  
Vibrational Relaxation ◽  
Precise Measure ◽  
Derivatives Of ◽  
Relaxing Gas ◽  
Flow Case

The breakdown of the characteristics solution in the neighbourhood of the leading frozen characteristic is investigated for the flow induced by a piston advancing with finite acceleration into a relaxing gas and for the steady supersonic flow of a relaxing gas into a smooth compressive corner. It is found that the point of breakdown moves outwards along the leading characteristic as the relaxation time decreases and that there is no breakdown of the solution on the leading characteristic if the gas has a sufficiently small, but non-zero, relaxation time. A precise measure of this relaxation time is derived. The paper deals only with points of breakdown determined by initial derivatives of the piston path or wall shape. In the steady-flow case, the Mach number based on the frozen speed of sound must be greater than unity.

The Properties of the Flow in an Elastic Duct

1985 ◽  
Author(s):  
You-Hai Wei ◽  
Xi-Chang Mao ◽  
Ren Fang
Keyword(s):  
Heat Transfer ◽  
Mach Number ◽  
Speed Of Sound ◽  
Critical Condition ◽  
Main Property ◽  
Critical Section ◽  
Area Change ◽  
Friction Heat

The flow in an elastic duct has some special properties. The speed of sound in this kind of flow is discovered to be smaller than in the flow in a rigid duct. Since the speed of sound decreases, flows which include area change, friction, heat transfer and mass addition reach the critical condition at Mach number less than one (M=1). It is particularly interesting that in a flow with area change the critical section doesn’t coincide with the minimum section. The main property of the flow in an elastic duct, that is the speed of sound being smaller than the traditional one, has been proved by experiment.

scholarly journals Semiconservative reduced speed of sound technique for low Mach number flows with large density variations

2019 ◽  
Vol 622 ◽  
pp. A157 ◽  
Author(s):  
H. Iijima ◽  
H. Hotta ◽  
S. Imada
Keyword(s):  
Mach Number ◽  
Speed Of Sound ◽  
Mass Density ◽  
Low Mach Number ◽  
Efficient Simulation ◽  
Large Density ◽  
Background Density ◽  
Density Perturbations ◽  
Volume Method ◽  
Numerical Domain

Context. The reduced speed of sound technique (RSST) has been used for efficient simulation of low Mach number flows in solar and stellar convection zones. The basic RSST equations are hyperbolic and are suitable for parallel computation by domain decomposition. The application of RSST is limited to cases in which density perturbations are much smaller than the background density. In addition, nonconservative variables are required to be evolved using this method, which is not suitable in cases where discontinuities such as shock waves coexist in a single numerical domain. Aims. In this study, we suggest a new semiconservative formulation of the RSST that can be applied to low Mach number flows with large density variations. Methods. We derive the wave speed of the original and newly suggested methods to clarify that these methods can reduce the speed of sound without affecting the entropy wave. The equations are implemented using the finite volume method. Several numerical tests are carried out to verify the suggested methods. Results. The analysis and numerical results show that the original RSST is not applicable when mass density variations are large. In contrast, the newly suggested methods are found to be efficient in such cases. We also suggest variants of the RSST that conserve momentum in the machine precision. The newly suggested variants are formulated as semiconservative equations, which reduce to the conservative form of the Euler equations when the speed of sound is not reduced. This property is advantageous when both high and low Mach number regions are included in the numerical domain. Conclusions. The newly suggested forms of RSST can be applied to a wider range of low Mach number flows.

Transonic Buffeting on Aerofoils

1960 ◽  
Vol 64 (599) ◽  
pp. 683-686 ◽  
Author(s):  
C. J. Wood
Keyword(s):  
Mach Number ◽  
Supersonic Flow ◽  
Speed Of Sound ◽  
Sudden Increase ◽  
Loss Of Control ◽  
Mixed Flow ◽  
Critical Mach Number ◽  
Control Effectiveness

There are many problems to be solved when it is required to fly an aircraft at speeds approaching the speed of sound. When the speed of the aeroplane exceeds its critical Mach number, regions of supersonic flow appear at points on its surface, where the velocity of the displaced air is greatest. These regions of supersonic flow increase in size with increasing speed until the flow is wholly supersonic. The range of speed in which this mixed flow occurs is called the transonic range. In this range an aircraft will experience a sudden increase in drag, trim changes, loss of control effectiveness and possibly instability, or buffeting.

On the irregular refraction of a plane shock wave at a Mach number interface

1968 ◽  
Vol 32 (1) ◽  
pp. 185-202 ◽  
Author(s):  
L. F. Henderson ◽  
A. K. Macpherson
Keyword(s):  
Shock Wave ◽  
Mach Number ◽  
Speed Of Sound ◽  
Expansion Wave ◽  
Plane Shock Wave ◽  
Plane Shock ◽  
Irregular Wave ◽  
Self Similar ◽  
Irregular Systems ◽  
Mach Reflexion

The paper considers the refraction of a plane shock wave at an interface between two streams of different Mach number. Particular attention is paid to the irregular wave systems. It is found that when the interface is slow-fast, that is when the speed of sound a0 in the first or incident wave medium is less than the speed of sound aB in the second or transmitted wave medium, then there are two irregular systems, one being a double Mach reflexion type and the other being a four-wave confluence type. There are also two irregular systems when the refraction is fast-slow; these are a single Mach reflexion type and an expansion wave type. This last system has a central expansion wave when the flow is steady and a continuous band expansion wave when the flow is self-similar. Only two of the irregular wave systems have been observed experimentally in the fully developed state. Possible degeneracies are discussed.

The Speed of Sound and Mach Number Effects

1964 ◽  
Vol 68 (643) ◽  
pp. 485-487 ◽  
Author(s):  
W. G. Watson
Keyword(s):  
Mach Number ◽  
Speed Of Sound

Since I have not been concerned with matters thermo-dynamic for some years, I have hesitated to enter the lists on the recent discussions on “The Speed of Sound and Mach Number Effects,” but I cannot let the comments of Mr. Naylor (Journal, January 1964, p. 63) and the reply by Messrs. Bragg and Smith stand without further comment.I am in agreement with Mr. Naylor in the specific circumstances with which he deals, but I believe his concentration upon the polytropic efficiency obscures the more fundamental approach.

The Speed of Sound and Mach Number Effects

1964 ◽  
Vol 68 (637) ◽  
pp. 63-63 ◽  
Author(s):  
V. D. Naylor
Keyword(s):  
Mach Number ◽  
Physical Interpretation ◽  
Speed Of Sound ◽  
Propagation Velocity ◽  
Rational Parameter ◽  
The Given

In a recent paper the suggestion is made that “it would be sensible when discussing the flow to use a Mach number based on the actual propagation velocity in the given circumstances.”This directs attention to the deeper question of whether or not a Mach number however defined is a rational parameter in terms of which to express effects of flow.In certain cases the quantity γp/ρ occurs quite naturally, regardless of any physical interpretation that can be given to it.

Assessment of Compressible RANS and LES Methods for Organic Vapor Flows Past a NACA4412 Airfoil

2019 ◽  
Author(s):  
Karsten Hasselmann ◽  
Stefan aus der Wiesche ◽  
Eugeny Y. Kenig
Keyword(s):  
Mach Number ◽  
Speed Of Sound ◽  
Gas Flow ◽  
Stokes Equations ◽  
Working Fluid ◽  
Vapor Flow ◽  
Real Gas ◽  
Critical Mach Number ◽  
The Real ◽  
Organic Vapor

Abstract In this contribution, an assessment of compressible Reynolds Averaged Navier Stokes equations (RANS) and Large Eddy Simulation (LES) is presented using transonic organic vapor flow past a NACA4412 airfoil as a case study. The NACA4412 represents a canonical geometry, which, in case of air, has been well investigated numerically and experimentally. The results of the real gas simulations are compared with those of air simulations. For the real gas, the organic vapor Novec 649® is chosen as a representative fluid. The thermodynamic behavior of Novec 649® is modeled with the Peng-Robinson equation of state. Different inlet Mach numbers are applied, namely, a sub-critical, the critical, and a super-critical Mach number. It turns out, that the critical Mach number of the NACA4412 airfoil increases when Novec 649® is used as working fluid. Furthermore, it is shown that real gas flow simulations cause additional difficulties for the computational fluid dynamics (CFD) analysis. Although the speed of sound of Novec 649® is lower than the speed of sound of air, a finer grid resolution is required for the real gas simulations due to its high density. Based on an extensive simulation study, an assessment of different numerical modelling strategies and methods is given.

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