scholarly journals Direct Numerical Simulation of Real-gas Effects within Turbulent Boundary Layers for Fully-developed Channel Flows

2021 ◽  
Vol 5 ◽  
pp. 216-232
Author(s):  
Tao Chen ◽  
Bijie Yang ◽  
Miles Robertson ◽  
Ricardo Martinez-Botas
Keyword(s):  
Outer Layer ◽  
Gas Flow ◽  
Reynolds Shear Stress ◽  
Turbulent Viscosity ◽  
Spanwise Direction ◽  
Real Gas ◽  
The Real ◽  
Real Gas Effect ◽  
Real Gas Effects ◽  
Gas Effect

Real-gas effects have a significant impact on compressible turbulent flows of dense gases, especially when flow properties are in proximity of the saturation line and/or the thermodynamic critical point. Understanding of these effects is key for the analysis and improvement of performance for many industrial components, including expanders and heat exchangers in organic Rankine cycle systems. This work analyzes the real-gas effect on the turbulent boundary layer of fully developed channel flow of two organic gases, R1233zd(E) and MDM - two candidate working fluids for ORC systems. Compressible direct numerical simulations (DNS) with real-gas equations of state are used in this research. Three cases are set up for each organic vapour, representing thermodynamic states far from, close to and inside the supercritical region, and these cases refer to weak, normal and strong real-gas effect in each fluid. The results within this work show that the real-gas effect can significantly influence the profile of averaged thermodynamic properties, relative to an air baseline case. This effect has a reverse impact on the distribution of averaged temperature and density. As the real-gas effect gets stronger, the averaged centre-to-wall temperature ratio decreases but the density drop increases. In a strong real-gas effect case, the dynamic viscosity at the channel center point can be lower than at channel wall. This phenomenon can not be found in a perfect gas flow. The real-gas effect increases the normal Reynolds stress in the wall-normal direction by 7–20% and in the spanwise direction by 10–21%, which is caused by its impact on the viscosity profile. It also increases the Reynolds shear stress by 5–8%. The real-gas effect increases the turbulence kinetic energy dissipation in the viscous sublayer and buffer sublayer <inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mo stretchy="false">(</mml:mo><mml:msup><mml:mi>y</mml:mi><mml:mo>∗</mml:mo></mml:msup><mml:mo><</mml:mo><mml:mn>30</mml:mn><mml:mo stretchy="false">)</mml:mo></mml:math></inline-formula> but not in the outer layer. The turbulent viscosity hypthesis is checked in these two fluids, and the result shows that the standard two-function RANS model (<inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mi>k</mml:mi><mml:mo>−</mml:mo><mml:mi>ϵ</mml:mi></mml:math></inline-formula> and <inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mi>k</mml:mi><mml:mo>−</mml:mo><mml:mi>ω</mml:mi></mml:math></inline-formula>) with a constant <inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:msub><mml:mi>C</mml:mi><mml:mi>μ</mml:mi></mml:msub><mml:mo>=</mml:mo><mml:mn>0.09</mml:mn></mml:math></inline-formula> is still suitable in the outer layer <inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mo stretchy="false">(</mml:mo><mml:msup><mml:mi>y</mml:mi><mml:mo>∗</mml:mo></mml:msup><mml:mo>></mml:mo><mml:mn>70</mml:mn><mml:mo stretchy="false">)</mml:mo></mml:math></inline-formula>, with an error in ±10%.

Real Gas Effect on Gas Slippage Phenomenon in Shale

2021 ◽  
Author(s):  
Yufei Chen ◽  
Juliana Y. Leung ◽  
Changbao Jiang ◽  
Andrew K. Wojtanowicz
Keyword(s):  
Pore Size ◽  
Free Path ◽  
Mean Free Path ◽  
Real Gas ◽  
The Real ◽  
Gas Slippage ◽  
Real Gas Effect ◽  
Shale Reservoirs ◽  
Low Pressures ◽  
Gas Effect

Abstract The past decade has seen the rapid development of shale gas across the world, as the record-breaking success and on-going surge of commercial shale gas production in such unconventional reservoirs pose a tremendous potential to meet the global energy supply. However, questions have been raised about the intricate gas transport mechanisms in the shale matrix, of which the gas slippage phenomenon is one of the key mechanisms for enhancing the fluid transport capacity and, therefore, the overall gas production. Given that shale reservoirs are often naturally deposited in the deep underground formations at high pressure and temperature conditions (much deeper than most typical conventional deposits), the real gas effect cannot be ignored as gas properties may vary significantly under such conditions. The purpose of this study is thus to investigate the real gas effect on the gas slippage phenomenon in shale by taking into account the gas compressibility factor (Z) and Knudsen number (Kn). This study begins with a specific determination of Z for natural gas at various pressures and temperatures under the real gas effect, followed by several calculations of the gas molecular mean free path at in-situ conditions. Following this, the real gas effect on gas slippage phenomenon in shale is specifically analyzed by examining the change in Knudsen number. Also discussed are the permeability deviation from Darcy flux (non-Darcy flow) due to the combination of gas slippage and real gas effect and the specific range of pressure and pore size for gas slippage phenomenon in shale reservoirs. The results show that the gas molecular mean free path generally increases with decreasing pressure, especially at relatively low pressures (&lt; 20 MPa). And, increasing temperature will cause the gas molecular mean free path to rise, also at low pressures. Knudsen number of an ideal gas is greater than that of a real gas; while lower than that of a real gas as pressure continues to rise. That is, the real gas effect suppresses the gas slippage phenomenon at low pressures, while enhancing it at high pressures. Also, Darcy’s law starts deviating when Kn &gt; 0.01 and becomes invalid at high Knudsen numbers, and this deviation increases with decreasing pore size. No matter how pore size varies, this deviation increases with decreasing pressure, meaning that the gas slippage effect is significant at low pressures. Finally, slip flow dominates in the various gas transport mechanisms given the typical range of pressure and pore size in shale reservoirs (1 MPa &lt; P &lt; 80 MPa; 3 nm &lt; d &lt; 3000 nm). Gas transport in shale is predominantly controlled by the slippage effect that mostly occurs in micro- or meso-pores (10 to 200 nm). Moreover, considering the real gas effect would improve the accuracy for determining the specific pressure range of the gas slippage phenomenon in shale.

scholarly journals Numerical Simulation of a GH2/LOx Single Injector Combustor and the Effect of the Turbulent Schmidt Number

Energies ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 6616
Author(s):  
Won-Sub Hwang ◽  
Woojoo Han ◽  
Kang Y. Huh ◽  
Juhoon Kim ◽  
Bok Jik Lee ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Schmidt Number ◽  
Liquid Oxygen ◽  
Temperature Profiles ◽  
Flamelet Model ◽  
Real Gas ◽  
The Real ◽  
Real Gas Effect ◽  
Turbulent Schmidt Number ◽  
Gas Effect

A large-eddy simulation (LES) of a gaseous hydrogen/liquid oxygen (GH2/LOX) single-injector rocket combustor is performed in this study. The Redlich–Kwong–Peng–Robinson (RK–PR) equation of state is used to simulate the real-gas effect under high-pressure conditions, and the steady laminar flamelet model (SLFM) is implemented to simulate fast chemistry, such as a H2/O2 reaction. From the numerical simulation, the characteristics of time-averaged flow and flame fields are obtained, and their relationship with the real-gas effect is investigated. It is possible to investigate unsteady flame features and the mixing mechanism of propellants in detail by examining multiple snapshots of the field contour. Another purpose of the study is to investigate the differences in flow and flame structures according to the variation in the turbulent Schmidt number. By comparing the simulation result with the natural OH* emission image and temperature profiles from experimental data, the appropriate range of the turbulent Schmidt number for the simulation is obtained. Furthermore, this paper suggests the usefulness and validity of the current research by quantitatively comparing (i.e., temperature profiles) numerical results with those of existing literature.

DSMC study of the real gas effect on lateral jet interaction of THAAD-like missile

2019 ◽  
Author(s):  
Dongming Ding ◽  
Hao Chen ◽  
Xiaoyu Shao ◽  
Bin Zhang ◽  
Hong Liu
Keyword(s):  
Real Gas ◽  
Jet Interaction ◽  
The Real ◽  
Real Gas Effect ◽  
Gas Effect

The real-gas effect in single-bubble sonoluminescence

1999 ◽  
Vol 4 (1) ◽  
pp. 29-34
Author(s):  
Li Yuan ◽  
Wei Wei ◽  
Cunyan Ho ◽  
Mingchung Chu ◽  
Puitang Leung
Keyword(s):  
Single Bubble ◽  
Real Gas ◽  
The Real ◽  
Real Gas Effect ◽  
Single Bubble Sonoluminescence ◽  
Gas Effect

scholarly journals Approximate Method for Calculating the Pressure Change in a Nonequilibrium-Deformable Reservoir in the Case of Real Gas Flow to the Well

2021 ◽  
Vol 135 (4) ◽  
pp. 36-39
Author(s):  
B. Z. Kazymov ◽  
◽  
K. K. Nasirova ◽  
Keyword(s):  
Approximate Method ◽  
Gas Flow ◽  
Pressure Change ◽  
Reservoir Pressure ◽  
Gas Reservoir ◽  
Real Gas ◽  
The Real ◽  
Over Time

A method is proposed for determining the distribution of reservoir pressure over time in a nonequilibrium-deformable gas reservoir in the case of real gas flow to the well under different technological conditions of well operation, taking into account the real properties of the gas and the reservoir.

The performance of spiral groove dry gas seal under choked flow condition considering the real gas effect

2019 ◽  
Vol 234 (4) ◽  
pp. 554-566
Author(s):  
Hengjie Xu ◽  
Pengyun Song ◽  
Wenyuan Mao ◽  
Qiangguo Deng
Keyword(s):  
Carbon Dioxide ◽  
Flow Condition ◽  
Ideal Gas ◽  
Leakage Rate ◽  
Spiral Groove ◽  
Real Gas ◽  
Dry Gas Seal ◽  
Choked Flow ◽  
Real Gas Effect ◽  
Gas Effect

By taking carbon dioxide and hydrogen as lubricating gas, respectively, this paper presents an analysis on the pressure characteristics and temperature distribution of spiral groove dry gas seal which influenced by real gas effect under choked flow condition. Numerical results show that the deviation between real gas and ideal gas, which expressed by the deviation degree between compressibility factor Z and 1, is the main reason for real gas effect affecting sealing performance. Compared with ideal gas model, real gas effect raises exit pressure, opening force, leakage rate, Mach number in dam region, and temperature for carbon dioxide ( Z < 1), while it decreases those characteristics for hydrogen ( Z > 1) under the same operating conditions. In addition, choked flow effect increases opening force and reduces leakage rate and temperature-drop between entrance and exit of sealing clearance. Meanwhile, it may cause an unstable behavior for the seal.

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