Towards unified CFD simulations of real fluid flows

2001 ◽  
Author(s):  
Jack Edwards
Keyword(s):  
Fluid Flows ◽  
Cfd Simulations ◽  
Real Fluid

Dynamics of Pipes Conveying Fluid With a Non-Uniform Velocity Profile

2009 ◽  
Author(s):  
Aren M. Hellum ◽  
Ranjan Mukherjee ◽  
Andrew J. Hull
Keyword(s):  
Velocity Profile ◽  
Critical Frequency ◽  
Fluid Flows ◽  
Drop Out ◽  
Total System ◽  
Number Range ◽  
Uniform Velocity ◽  
Real Fluid ◽  
Uniform Case ◽  
Conveying Fluid

Previous work on stability of fluid-conveying cantilever pipes assumed a uniform velocity profile for the conveyed fluid. In real fluid flows, the presence of viscosity leads to a sheared region near the wall. Earlier studies correctly note that viscous forces drop out of the system’s dynamics since the force of fluid shear on the wall is precisely balanced by pressure drop in the conveyed fluid. The effect of shear has therefore not been ignored in these studies. However, a uniform velocity profile assumes that the sheared region is infinitely thin. Prior analysis was extended to account for a fully developed non-uniform profile such as would be encountered in real fluid flows. A modified equation of motion was derived to account for the reduced momentum carried by the sheared fluid. Numerical analysis was carried out to determine a number of velocity profiles over the Reynolds number range of interest and a simple set of curve fits was used when finer discretization was required. Stability analysis of a pipe conveying fluid with these profiles was performed, and the results were compared to a uniform profile. The mass ratio, β, is the ratio of the fluid mass to the total system mass. At β = 0.2, the non-uniform case becomes unstable at a critical velocity, ucr, that is 5.4% lower than the uniform case. The critical frequency, fcr, is 0.36% higher than the uniform case. A more sensitive region exists near β = 0.32. There, the nonuniform velocity ucr is 23% lower than the uniform case and the non-uniform critical frequency fcr is 49% of the uniform case.

Numerical Simulation of Vortex Shedding From a Circular Cylinder in the Presence of a Free Surface

2003 ◽  
Author(s):  
S. Nagaya ◽  
R. E. Baddour
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Free Surface ◽  
Circular Cylinder ◽  
Vortex Shedding ◽  
Fluid Flows ◽  
Reynolds Numbers ◽  
Cfd Simulations ◽  
Induced Drag

CFD simulations of crossflows around a 2-D circular cylinder and the resulting vortex shedding from the cylinder are conducted in the present study. The capability of the CFD solver for vortex shedding simulation from a circular cylinder is validated in terms of the induced drag and lifting forces and associated Strouhal numbers computations. The validations are done for uniform horizontal fluid flows at various Reynolds numbers in the range 103 to 5×105. Crossflows around the circular cylinder beneath a free surface are also simulated in order to investigate the characteristics of the interaction between vortex shedding and a free surface at Reynolds number 5×105. The influence of the presence of the free surface on the vortex shedding due to the cylinder is discussed.

Low-Diffusion Flux-Splitting Methods for Real Fluid Flows with Phase Transitions

AIAA Journal ◽  
2000 ◽  
Vol 38 (9) ◽  
pp. 1624-1633 ◽  
Author(s):  
Jack R. Edwards ◽  
Randall K. Franklin ◽  
Meng-Sing Liou
Keyword(s):  
Phase Transitions ◽  
Diffusion Flux ◽  
Fluid Flows ◽  
Splitting Methods ◽  
Flux Splitting ◽  
Real Fluid

Quasi-1D Unsteady Conjugate Module for Rocket Engine and Propulsion System Simulations

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Bryan T. Campbell ◽  
Roger L. Davis
Keyword(s):  
Transient Flow ◽  
Rocket Engine ◽  
Fluid Flows ◽  
Solution Procedure ◽  
Test Cases ◽  
Rocket Engines ◽  
Propulsion Systems ◽  
One Dimensional ◽  
Real Fluid ◽  
Software Modules

A new quasi-one-dimensional procedure (one-dimensional with area change) is presented for the transient solution of real-fluid flows in lines and volumes including heat transfer effects. The solver will be integrated into a larger suite of software modules developed for simulating rocket engines and propulsion systems. The solution procedure is coupled with a state-of-the-art real-fluid property database so that both compressible and incompressible fluids may be considered using the same procedure. The numerical techniques used in this procedure are described. Test cases modeling transient flow of nitrogen, water, and hydrogen are presented to demonstrate the capability of the current technique.

Remarks on Snow Cornice Theory and Related Experiments With Sink Flows

1966 ◽  
Vol 88 (2) ◽  
pp. 539-547 ◽  
Author(s):  
Gunnar Heskestad
Keyword(s):  
Experimental Verification ◽  
Fluid Flows ◽  
Real Fluid

A review is made of Ringleb’s theory on snow cornice-like flows and of the published, unsuccessful attempts at experimental verification. Arguments are presented which render the theory an unlikely representation of real fluid flows. The flow over a downstream-facing step in a channel, with either of two types of sinks located immediately downstream of the step, was investigated experimentally. A vortex and associated smooth expansion of the exterior flow behind the step were established for sufficiently high sink rates. A model of the step-sink flow is suggested and found consistent with results presented here and elsewhere.

Low-diffusion flux-splitting methods for real fluid flows with phase transitions

AIAA Journal ◽  
2000 ◽  
Vol 38 ◽  
pp. 1624-1633 ◽  
Author(s):  
Jack R. Edwards ◽  
Randall K. Franklin ◽  
Meng-Sing Liou
Keyword(s):  
Phase Transitions ◽  
Diffusion Flux ◽  
Fluid Flows ◽  
Splitting Methods ◽  
Flux Splitting ◽  
Real Fluid

scholarly journals CFD Simulations of Two-Phase Gas/non-Newtonian Fluid Flows in Pipes

2018 ◽  
Author(s):  
Miguel A. Daza Gómez ◽  
Nicolás Ratkovich ◽  
Eduardo Pereyra ◽  
Pietro Poesio
Keyword(s):  
Newtonian Fluid ◽  
Fluid Flows ◽  
Cfd Simulations ◽  
Two Phase

Dynamics of Pipes Conveying Fluid With Non-Uniform Turbulent and Laminar Velocity Profiles

2010 ◽  
Author(s):  
Aren M. Hellum ◽  
Ranjan Mukherjee ◽  
Andrew J. Hull
Keyword(s):  
Reynolds Number ◽  
Velocity Profile ◽  
Parameter Space ◽  
Fluid Flows ◽  
Number Range ◽  
Uniform Velocity ◽  
Real Fluid ◽  
Viscous Shear ◽  
Pipes Conveying Fluid ◽  
Conveying Fluid

Previous analytical work on stability of fluid-conveying pipes assumed a uniform velocity profile for the conveyed fluid. In real fluid flows, the presence of viscosity leads to a sheared region near the wall. Earlier studies correctly note that viscous forces do not affect the dynamics of the system since these forces are balanced by pressure drop in the conveyed fluid. Although viscous shear has not been ignored in these studies, a uniform velocity profile assumes that the sheared region is infinitely thin. Prior analysis was extended to account for a fully developed nonuniform profile such as would be encountered in real fluid flows. A modified, highly tractable equation of motion was derived, which includes a single additional parameter to account for the true momentum of the fluid. This empirical parameter was determined by numerical analysis over the Reynolds number range of interest. The stability of cantilever pipes conveying fluid with two types of non-uniform velocity profile was assessed. In the first case, the profile was a function of Reynolds number and transition to turbulence occurred before the onset of flutter instability. This case had stability properties similar to the uniform velocity case except in specific narrow regions of the parameter space. The second case required that the Reynolds number be such that the flow was always laminar. For this case, lower fluid velocity was required to achieve instability, and the oscillation frequency at instability was considerably lower over much of the parameter space, compared to the uniform case.

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