Pressure Wave Generation in a Fissioning Gas. IV. Analysis by the Method of Characteristics

1966 ◽  
Vol 9 (12) ◽  
pp. 2357
Author(s):  
Walter N. Podney
Keyword(s):  
Pressure Wave ◽  
Method Of Characteristics ◽  
Wave Generation ◽  
The Method Of Characteristics

Fluid Compressibility Effects in Steam Hammer Analyses

2015 ◽  
Author(s):  
Beniamino Rovagnati ◽  
John H. Gray
Keyword(s):  
Incompressible Flow ◽  
Sound Speed ◽  
Pressure Wave ◽  
Method Of Characteristics ◽  
Wave Length ◽  
Valve Closure ◽  
The Method Of Characteristics ◽  
Fluid Transient ◽  
Transient Loads ◽  
Compressibility Effects

In the power industry, steam hammer piping analyses (and fluid transient loads) are often based on incompressible flow principles. Consequently, it is common to use either computer programs based on the Method of Characteristics for incompressible flow or simple hand calculations such as that described by E. C. Goodling (ASME PVP, Vol. 149–157, 1989). Goodling’s paper provides a simplified method to visualize and estimate transient loads resulting from stop valve closure in a main steam system. To account for compressibility effects, the calculated loads are sometimes adjusted by using a correction factor directly applied to the fluid loads with the fluid sound speed assumed constant in time and space. For example, Goodling’s paper suggests that a load increase of 5% may be used. In this paper, a sample steam hammer problem is solved using the Method of Characteristics for compressible flows, where the fluid is assumed to behave as a perfect gas. The effects of steam compressibility are then discussed. Specifically the shortening of the characteristic valve closure pressure wave length, resulting from the increasing magnitude of the sound speed as the pressure wave moves upstream from the closing valve, and resulting higher loads in straight pipe segments shorter than the pressure wave length, are then discussed. It is shown that in these shorter pipe segments fluid transient loads may almost double those calculated using the MOC for incompressible flows or the Goodling methodology (without correction factors) if the distance upstream from the closing valve is of sufficient length.

An Introduction to the Dynamic Pressure Exchanger

1965 ◽  
Vol 180 (1) ◽  
pp. 451-480 ◽  
Author(s):  
P. H. Azoury
Keyword(s):  
Pressure Wave ◽  
Method Of Characteristics ◽  
Dynamic Pressure ◽  
Pressure Ratio ◽  
Historical Background ◽  
The Method Of Characteristics ◽  
Wave Effects ◽  
Recent Developments ◽  
A Cell ◽  
Secondary Fluid

The historical background and operational principle of the Dynamic Pressure Exchanger (DPE) are outlined. The basic aerodynamic processes of cell-emptying and cell-filling are analysed by the ‘method of characteristics’ for air and for no temperature discontinuities in the unsteady flow pattern. The results of the analysis are then used to generalize performance qualitatively for overall pressure ratios up to the sonic threshold. It is shown that, for pressure wave effects to be fully utilized, a DPE rotor should run such that 8 is of the order of or less than 0.5, where δ is the ratio of the time taken to open or close a cell to the time taken for a sound wave to travel a cell length at the thermodynamic stagnation state of the primary or secondary fluid. In the case where the thermodynamic properties of the fluids vary considerably, it is suggested that 8 be referred to the gas which yields the highest sonic speed. In general, the extent to which the performance is affected by a change in δ, within the range 0 < δ < 0.5, is inappreciable. It is also shown that the use of a transfer passage may be expected to yield a significant improvement in performance and an increased range in overall pressure ratio. A number of applications are described and some recent developments are reviewed. It is also indicated that the main sources of loss can be incorporated within the method of characteristics used in the prediction of performance.

Non-symmetric flow in Laval type nozzles

1972 ◽  
Vol 273 (1232) ◽  
pp. 185-235 ◽  
Keyword(s):  
Steady State ◽  
Combustion Chamber ◽  
Method Of Characteristics ◽  
Three Dimensions ◽  
Symmetric Flow ◽  
Gaseous Flow ◽  
The Method Of Characteristics ◽  
Lateral Forces

The equations of the steady state, compressible inviscid gaseous flow are linearized in a form suitable for application to nozzles of the Laval type. The procedure in the supersonic phase is verified by comparing solutions so obtained with those derived by the method of characteristics in two and three dimensions. Likewise, the solutions in the transonic phase are com pared with those obtained by other investigators. The linearized equation is then used to investigate the nat re of non-symmetric flow in rocket nozzles. It is found that if the flow from the combustion chamber into the nozzle is non-symmetric, the magnitude and direction of the turning couple produced by the emergent jet is dependent on the profile of the nozzle and it is possible to design profiles such that the turning couples or lateral forces are zero. The optimum nozzle so designed is independent of the pressure and also of the magnitude of the non-symmetry of the entry flow. The formulae by which they are obtained have been checked by extensive static and projection tests with simulated rocket test vehicles which are described in this paper.

Boundary Layer Closure and Heat Transfer in Constant Base Pressure and Simple Wave Guns

1978 ◽  
Vol 100 (4) ◽  
pp. 690-696 ◽  
Author(s):  
A. D. Anderson ◽  
T. J. Dahm
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Method Of Characteristics ◽  
Simple Wave ◽  
Momentum Equation ◽  
Base Pressure ◽  
Two Dimensional ◽  
The Method Of Characteristics

Solutions of the two-dimensional, unsteady integral momentum equation are obtained via the method of characteristics for two limiting modes of light gas launcher operation, the “constant base pressure gun” and the “simple wave gun”. Example predictions of boundary layer thickness and heat transfer are presented for a particular 1 in. hydrogen gun operated in each of these modes. Results for the constant base pressure gun are also presented in an approximate, more general form.

scholarly journals Numerical Boundary Conditions for Solar Magnetic Hydrodynamic Flows Using the Method of Characteristics

1996 ◽  
Vol 154 ◽  
pp. 149-153
Author(s):  
S. T. Wu ◽  
A. H. Wang ◽  
W. P. Guo
Keyword(s):  
Boundary Conditions ◽  
Method Of Characteristics ◽  
Numerical Solutions ◽  
The Self ◽  
Time Dependent ◽  
Solar Plasma ◽  
The Method Of Characteristics ◽  
Mhd Simulations ◽  
Self Consistent ◽  
Dynamic Structures

AbstractWe discuss the self-consistent time-dependent numerical boundary conditions on the basis of theory of characteristics for magnetohydrodynamics (MHD) simulations of solar plasma flows. The importance of using self-consistent boundary conditions is demonstrated by using an example of modeling coronal dynamic structures. This example demonstrates that the self-consistent boundary conditions assure the correctness of the numerical solutions. Otherwise, erroneous numerical solutions will appear.

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