Mach Number on Outlet Plane of a Straight Micro-Tube

2013 ◽  
Author(s):  
Y. Asako ◽  
D. Kawashima ◽  
T. Yamada ◽  
C. Hong
Keyword(s):  
Mach Number ◽  
Turbulent Flow ◽  
Gas Flow ◽  
Flow Characteristics ◽  
Ideal Gas ◽  
Computational Domain ◽  
Arbitrary Lagrangian Eulerian ◽  
Downstream Region ◽  
Laminar And Turbulent Flow ◽  
Energy Equations

The Mach number and pressure on the outlet plane of a straight micro-tube were investigated numerically for both laminar and turbulent flow cases. The numerical methodology is based on the Arbitrary-Lagrangian-Eulerian (ALE) method. The LB1 turbulence model was used for the turbulent flow case. The compressible momentum and energy equations with the assumption of the ideal gas were solved. The computational domain is extended to the downstream region from the micro-tube outlet. The back pressure was given to the outside of the downstream region. The computations were performed for a tube whose diameter ranges from 50 to 500 μm. The average Mach number on the outlet plane of the fully under-expanded flow depends on the tube diameter and ranges from 1.16 to 1.25. The flow characteristics of the under-expanded gas flow in a straight micro-tube were revealed.

Mach number at outlet plane of a straight micro-tube

2016 ◽  
Vol 230 (19) ◽  
pp. 3420-3430 ◽  
Author(s):  
D Kawashima ◽  
T Yamada ◽  
C Hong ◽  
Y Asako
Keyword(s):  
Mach Number ◽  
Turbulent Flow ◽  
Gas Flow ◽  
Flow Characteristics ◽  
Ideal Gas ◽  
Computational Domain ◽  
Arbitrary Lagrangian Eulerian ◽  
Choked Flow ◽  
Downstream Region ◽  
Energy Equations

The Mach number and pressure at the outlet plane of a straight micro-tube were investigated numerically for both laminar and turbulent flow cases. The numerical methodology is based on the arbitrary Lagrangian-Eulerian method. The LB1 turbulence model was used for the turbulent flow case. The compressible momentum and energy equations with the assumption of the ideal gas were solved. The computational domain is extended to the downstream region from the micro-tube outlet. The back pressure was given to the outside of the downstream region. The computations were performed for a tube whose diameter ranges from 50 to 500 μm. The average Mach number at the outlet plane of the choked flow depends on the tube diameter and ranges from 1.16 to 1.25. The flow characteristics of the under-expanded gas flow in a straight micro-tube were revealed.

Effect of Compressibility on Gaseous Flows in a Micro-Tube

2003 ◽  
Author(s):  
Yutaka Asako ◽  
Kenji Nakayama
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Pressure Distribution ◽  
Flow Characteristics ◽  
Fused Silica ◽  
Two Dimensional ◽  
Arbitrary Lagrangian Eulerian ◽  
Gaseous Flow ◽  
Gaseous Flows ◽  
Energy Equations

The product of friction factor and Reynolds number (f·Re) of gaseous flow in the quasi-fully developed region of a micro-tube was obtained experimentally and numerically. The tube cutting method was adopted to obtain the pressure distribution along the tube. The fused silica tubes whose nominal diameters were 100 and 150 μm, were used. Two-dimensional compressible momentum and energy equations were solved to obtain the flow characteristics in micro-tubes. The numerical methodology is based on the Arbitrary-Lagrangian-Eulerian (ALE) method. The both results agree well and it was found that (f·Re) is a function of Mach number.

Convective Heat Transfer of Unchoked and Choked Gas Flow in Micro-Tubes

2014 ◽  
Author(s):  
Chungpyo Hong ◽  
Yutaka Asako
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulent Flow ◽  
Wall Temperature ◽  
Gas Flow ◽  
Stagnation Pressure ◽  
Bulk Temperature ◽  
Stagnation Temperature ◽  
Computational Domain ◽  
Downstream Region

Heat transfer characteristics of unchoked and choked gas flows in micro-tubes with constant wall temperature were numerically investigated both laminar and turbulent flow cases. The numerical methodology is based on the Arbitrary-Lagrangian-Eulerian (ALE) method. The Lam-Bremhorst Low-Reynolds number turbulence model was used for turbulent flow. The compressible momentum and energy equations with the assumption of the ideal gas were solved. The computational domain should be extended to the downstream region of the hemisphere from micro-tube outlet. The back pressure was given to the outside of the downstream region. The stagnation temperature is fixed at 300K and the computations were done for the wall temperature which ranges from 305K to 350K. The tube diameter ranges from 50 to 250 μm and tube aspect ratio is 200. The stagnation pressure is chosen in such a way that the flow at micro-tube exit is enough to be fully under-expanded. By increasing the stagnation pressure, the internal flow in the micro-tube is choked and the flow at the micro-tube outlet is under-expanded. Although the velocity remains constant, the mass flow rate (Reynolds number) increases. The results in a wide range of Reynolds number and Mach number were obtained. The bulk temperature based on the static temperature and the total temperature are compared with those of the incompressible flow. A correlation for the prediction of the heat transfer rate of the unchoked and choked gas flow in micro-tubes is proposed.

Investigating the entropy generation around an airfoil in turbulent flow

2020 ◽  
Vol 92 (7) ◽  
pp. 1001-1017
Author(s):  
Mohammad Reza Saffarian ◽  
Farzad Jamaati ◽  
Amin Mohammadi ◽  
Fatemeh Gholami Malekabad ◽  
Kasra Ayoubi Ayoubloo
Keyword(s):  
Mach Number ◽  
Turbulent Flow ◽  
Turbulence Model ◽  
Entropy Generation ◽  
Turbulent Regime ◽  
Content Type ◽  
Sst Turbulence Model ◽  
Effects Of Temperature ◽  
Energy Equations ◽  
Naca 0012

Purpose This study aims to evaluate the amount of entropy generation around the NACA 0012 airfoil. This study takes place in four angles of attack of 0°, 5°, 10° and 16° and turbulent regime. Also, the variation in the amount of generated entropy by the changes in temperature and Mach number is investigated. Design/methodology/approach The governing equations are solved using computational fluid dynamics techniques. The continuity, momentum and energy equations and the equations of the SST k-ω turbulence model are solved. The entropy generation at different angles of attack is calculated and compared. The effect of various parameters in the generation of entropy is presented. Findings Results show that the major part of the entropy generation is at the tip of the airfoil. Also, increasing the angle of attack will increase the entropy generation. Also, results show that with increasing the temperature of air colliding with the airfoil, the production of entropy decreases. Originality/value Entropy generation is investigated in the NACA 0012 airfoil at various angles of attack and turbulent flow using the SST turbulence model. Also, the effects of temperature and Mach number on the entropy generation are investigated.

Experimental Investigations of Laminar, Transitional to Turbulent Gas Flow in a Micro-Channel

2010 ◽  
Author(s):  
Chungpyo Hong ◽  
Toru Yamada ◽  
Yutaka Asako ◽  
Mohammad Faghri ◽  
Koichi Suzuki ◽  
...  
Keyword(s):  
Mach Number ◽  
Flow Regime ◽  
Gas Flow ◽  
Flow Characteristics ◽  
Channel Length ◽  
Transitional Flow ◽  
Experimental Investigations ◽  
Compressibility Effect ◽  
Micro Channels ◽  
Wide Range

This paper presents experimental results on flow characteristics of laminar, transitional to turbulent gas flows through micro-channels. The experiments were performed for three micro-channels. The micro-channels were etched into silicon wafers, capped with glass, and their hydraulic diameter are 69.48, 99.36 and 147.76 μm. The pressure was measured at seven locations along the channel length to determine local values of Mach number and friction factor for a wide range of flow regime from laminar to turbulent flow. Flow characteristics in transitional flow regime to turbulence were obtained. The result shows that f·Re is a function of Mach number and higher than incompressible value due to the compressibility effect. The values of f·Re were compared with f·Re correlations in available literature.

Laminar and Turbulent Flow Past a Hydrofoil Predicted by a Distributed Vorticity Method

2020 ◽  
Author(s):  
Chunlin Wu ◽  
Spyros A. Kinnas
Keyword(s):  
Turbulent Flow ◽  
Eddy Viscosity ◽  
Current Method ◽  
Reynolds Numbers ◽  
Synchronous Communication ◽  
Coupling Scheme ◽  
Computational Domain ◽  
Computationally Efficient ◽  
Flow Past ◽  
Laminar And Turbulent Flow

Abstract A distributed viscous vorticity equation (VISVE) method is presented in this work to simulate the laminar and turbulent flow past a hydrofoil. The current method is proved to be more computationally efficient and spatially compact than RANS (Reynolds-Averaged Navier-Stokes) methods since this method does not require unperturbed far-field boundary conditions, which leads to a small computational domain, a small number of mesh cells, and consequently much less simulation time. To model the turbulent flow, a synchronous coupling scheme is implemented so that the VISVE method can resolve the turbulent flow by considering the eddy viscosity in the vorticity transport equation, and the eddy viscosity is obtained by coupling VISVE with the existing turbulence model of OpenFOAM, via synchronous communication. The proposed VISVE method is applied to simulate both the laminar flow at moderate Reynolds numbers and turbulent flow at high Reynolds numbers past a hydrofoil. The velocity and vorticity calculated by the coupling method agree well with the results obtained by a RANS method.

USING ATLAS OF HEART SHAPES FOR SIMULATION OF BLOOD FLOW IN LEFT VENTRICLE

2013 ◽  
Vol 25 (06) ◽  
pp. 1350050 ◽  
Author(s):  
Mir-Hossein Moosavi ◽  
Nasser Fatouraee ◽  
Hamid Katoozian ◽  
Ali Pashaei ◽  
Alejandro F. Frangi
Keyword(s):  
Blood Flow ◽  
Left Ventricle ◽  
Moving Boundary ◽  
Initial Conditions ◽  
Flow Characteristics ◽  
Computational Domain ◽  
Arbitrary Lagrangian Eulerian ◽  
Clinical Value ◽  
Aortic Sinus ◽  
Physiological Models

Integrative modeling of cardiac system is important for understanding the complex biophysical function of the heart]. To this end, multimodal cardiovascular imaging plays an important role in providing the computational domain, the boundary/initial conditions, and tissue function and properties. In particular, the incorporation of blood flow in the physiological models can help to simulate the hemodynamic properties and their effects on cardiac function. In this paper, we present a multimodal framework for quantitative and subject-specific analysis of blood flow in the cardiac chambers, including the left ventricle (LV). The 3D geometries of the LV at different time steps are extracted from medical images using an atlas of LV shape. The motion of the myocardium wall is used to extract the moving boundary data of the computational geometry. The data is used as a constraint for the computational fluid dynamics (CFD). An arbitrary Lagrangian–Eulerian (ALE) finite element method (FEM) formulation is used to derive a numerical solution of the transient dynamic equation of the fluid domain. With this method, simulation results describe detailed flow characteristics (such as velocity, pressure and wall shear stress) in the computational domain. The personalized hemodynamic characteristics obtained with the proposed approach can provide clinical value for diagnosis and treatment of abnormalities related to disturbed blood flow such as in myocardial remodeling and aortic sinus lesion formation.

Pressure loss of gaseous flow at a micro-tube outlet

2010 ◽  
Vol 225 (3) ◽  
pp. 649-657
Author(s):  
Y Horii ◽  
Y Asako ◽  
C Hong ◽  
J Lee
Keyword(s):  
Mach Number ◽  
Atmospheric Pressure ◽  
Pressure Loss ◽  
Stagnation Pressure ◽  
Loss Coefficient ◽  
Arbitrary Lagrangian Eulerian ◽  
Gaseous Flow ◽  
Pressure Loss Coefficient ◽  
Loss Coefficients ◽  
Energy Equations

The pressure loss of gaseous flow at a micro-tube outlet was investigated numerically. The numerical methodology is based on the arbitrary Lagrangian—Eulerian (ALE) method. Axis-symmetric compressible momentum and energy equations are solved to obtain the pressure loss coefficient of gaseous flow at a micro-tube outlet. Computed tube diameters are 50, 100, and 150μm. The stagnation pressure of upper stream of the tube is chosen in such a way that the Mach number at the tube outlet ranges from 0.1 to 1.2. The ambient (back) pressure is fixed at the atmospheric pressure. The pressure loss coefficients are compared with available experimental data for a conventionally sized tube. The effects of the Mach number and the tube diameter on the pressure loss coefficient are discussed and a correlation for the pressure loss coefficient is proposed.

scholarly journals Numerical Analysis of Turbulent Flow over a 2-D Prolate Spheroid

2019 ◽  
Vol 8 (4) ◽  
pp. 4646-4651
Keyword(s):  
Reynolds Number ◽  
Numerical Analysis ◽  
Turbulent Flow ◽  
Flow Characteristics ◽  
Prolate Spheroid ◽  
External Flow ◽  
Complex Phenomenon ◽  
Convective Flux ◽  
Viscous Forces ◽  
Laminar And Turbulent Flow

Recently external flow over body creates more interest of study because flow characteristics are dominated by complex phenomenon like separation and transition.in this paper turbulent flow over a 2-D prolate spheroid (6:1) is consider for analysis. Generation of surface grid around prolate spheroid by using grid generation code MESHGEN. Laminar and turbulent Flow past given geometry is simulated by Navier-stoke code RANS3D by second order upwind scheme for convective flux discretization by k-ε model for different Reynolds number, angles of attack .It is observed that the value of drag coefficient is lower than that of a cylinder due to its more streamlined contour. The variation of Cd was steeper in the laminar range than the turbulent range due to the effects of viscous forces being greater in laminar flow.

Friction Factor Correlations of Slip Flow in Micro-Tubes

2007 ◽  
Author(s):  
Chungpyo Hong ◽  
Yutaka Asako ◽  
Mohammad Faghri
Keyword(s):  
Mach Number ◽  
Friction Factor ◽  
Slip Flow ◽  
Constant Heat Flux ◽  
Arbitrary Lagrangian Eulerian ◽  
Constant Wall Temperature ◽  
Wide Range ◽  
Exit Mach Number ◽  
Poiseuille Number ◽  
Energy Equations

Poiseuille number, the product of friction factor and Reynolds number (f·Re) for quasi-fully developed flow in a micro-tube was obtained in slip flow regime. The numerical methodology is based on the Arbitrary-Lagrangian-Eulerian (ALE) method. Two-dimensional compressible momentum and energy equations were solved for a wide range of Reynolds and Mach numbers with two thermal boundary conditions: CWT (constant wall temperature) and CHF (constant heat flux), respectively. The tube diameter ranges from 3 to 10μm and the tube aspect ratio is 200. The stagnation pressure, pstg is chosen in such away that the exit Mach number ranges from 0.1 to 1.0. The outlet pressure is fixed at the atmospheric pressure. In slip flow, Mach and Knudsen numbers are systematically varied to determine their effects on f·Re. The correlation for f·Re is obtained from numerical results. It was found that f·Re is mainly a function of Mach number and Knudsen number and is different from the values obtained by 64/(1+8Kn) for slow flow. The obtained f·Re correlations are applicable to both no-slip and slip flow regimes.

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