A NUMERICAL STUDY OF FLUID INJECTION AND MIXING UNDER NEAR-CRITICAL CONDITIONS

2012 ◽  
Vol 19 ◽  
pp. 39-49 ◽  
Author(s):  
HUA-GUANG LI ◽  
XI-YUN LU ◽  
VIGOR YANG
Keyword(s):  
Reynolds Number ◽  
Shear Layer ◽  
Numerical Study ◽  
Ideal Gas ◽  
Critical Conditions ◽  
Reference Case ◽  
Nitrogen Injection ◽  
Volume Dilatation ◽  
High Reynolds ◽  
The Ideal

Nitrogen injection under conditions in close vicinity of liquid-gas critical point is studied through numerical simulation. The thermodynamic and transport properties of fluid exhibit anomalies in the near-critical fluid regime. These anomalies can cause distinctive effects on heat transfer and hydrodynamics. To focus on the influence of the highly variable properties and avoid the difficulties encountered in modeling high Reynolds number flows, a relatively low injection Reynolds number is adopted. A reference case with the same configuration and Reynolds number is also simulated in the ideal gas regime. Full conservation laws, real-fluid thermodynamic and transport phenomena are accommodated in the model. The obtained results reveal that the flow features of the near-critical fluid jet are significantly different from the ideal gas case. The near-critical fluid jet spreads faster and mixes better with the ambient fluid compared to the ideal gas jet. It is also identified that vortex pairing process develops faster in the near-critical case than in the ideal gas case. Detailed analysis of data at different streamwise positions including both flat shear layer region and fully developed vortex region reveals the effect of volume dilatation and baroclinic torque plays an important role in the near-critical fluid case. The volume dilatation effect disturbs the shear layer and makes it more unstable. The volume dilatation and baroclinic effects strengthen the vorticity and stimulate the vortex rolling up and pairing process.

Numerical Performance of Transition Models in Different Turbomachinery Flow Conditions: A Comparative Study

2000 ◽  
Author(s):  
Jiasen Hu ◽  
Torsten H. Fransson
Keyword(s):  
Reynolds Number ◽  
Pressure Gradient ◽  
Numerical Study ◽  
Adverse Pressure Gradient ◽  
Navier Stokes ◽  
Test Cases ◽  
Pressure Gradients ◽  
Flow Conditions ◽  
Transition Models ◽  
High Reynolds

A numerical study has been performed to compare the overall performance of three transition models when used with an industrial Navier-Stokes solver. The three models investigated include two experimental correlations and an integrated eN method. Twelve test cases in realistic turbomachinery flow conditions have been calculated. The study reveals that all the three models can work numerically well with an industrial Navier-Stokes code, but the prediction accuracy of the models depends on flow conditions. In general, all the three models perform comparably well to predict the transition in weak or moderate adverse pressure-gradient regions. The two correlations have the merit if the transition starts in strong favorable pressure-gradient region under high Reynolds number condition. But only the eN method works well to predict the transition controlled by strong adverse pressure gradients. The three models also demonstrate different capabilities to model the effects of turbulence intensity and Reynolds number.

Thin Shear Layer Structures in High Reynolds Number Turbulence

2013 ◽  
Vol 92 (3) ◽  
pp. 607-649 ◽  
Author(s):  
Julian C. R. Hunt ◽  
Takashi Ishihara ◽  
Nicholas A. Worth ◽  
Yukio Kaneda
Keyword(s):  
Reynolds Number ◽  
Shear Layer ◽  
High Reynolds Number ◽  
Layer Structures ◽  
High Reynolds

scholarly journals When is high Reynolds number shear flow not turbulent?

2017 ◽  
Vol 824 ◽  
pp. 1-4 ◽  
Author(s):  
Steven A. Balbus
Keyword(s):  
Reynolds Number ◽  
Shear Flow ◽  
High Reynolds Number ◽  
Laboratory Experiments ◽  
Numerical Study ◽  
Accretion Discs ◽  
Large Reynolds Number ◽  
Rotating Flow ◽  
General Tendency ◽  
High Reynolds

Rotating flow in which the angular velocity decreases outward while the angular momentum increases is known as ‘quasi-Keplerian’. Despite the general tendency of shear flow to break down into turbulence, this type of flow seems to maintain stability at very large Reynolds number, even when nonlinearly perturbed, a behaviour that strongly influences our understanding of astrophysical accretion discs. Investigating these flows in the laboratory is difficult because secondary Ekman flows, caused by the retaining Couette cylinders, can become turbulent on their own. A recent high Reynolds number numerical study by Lopez & Avila (J. Fluid Mech., vol. 817, 2017, pp. 21–34) reconciles apparently discrepant laboratory experiments by confirming that this secondary flow recedes toward the axial boundaries of the container as the Reynolds number is increased, a result that enhances our understanding of nonlinear quasi-Keplerian flow stability.

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