Viscous Flow Analysis in Mixed Flow Rotors

1980 ◽  
Vol 102 (1) ◽  
pp. 193-201 ◽  
Author(s):  
I. Khalil ◽  
W. Tabakoff ◽  
A. Hamed
Keyword(s):  
Viscous Flow ◽  
Stokes Equations ◽  
Flow Analysis ◽  
Flow Characteristics ◽  
Laminar Flows ◽  
Operating Conditions ◽  
Field Analysis ◽  
Navier Stokes ◽  
Stream Channels ◽  
Wide Range

A method for analyzing the viscous flow through turbomachine rotors is presented. The field analysis is based on the solution of the full Navier-Stokes equations over the rotor blade-to-blade stream channels. An Alternating-Direction-Implicit method is employed to carry out the necessary numerical integration of the elliptic governing equations. The flow analysis may be applied to various types of turbomachine rotors. Preliminarily, only the case of laminar flows are considered in this paper. The flow characteristics within the rotors of a radial inflow turbine and a radial bladed compressor are investigated over a wide range of operating conditions. Excellent results are obtained when compared with existing experimental data. The method of this analysis is quite general and can deal with wide range of applications. Possible modification of the present study to deal with turbulent flow cases are also identified.

Viscous Flow Analysis as a Design Tool for Hydraulic Turbine Components

1990 ◽  
Vol 112 (1) ◽  
pp. 5-11 ◽  
Author(s):  
T. C. Vu ◽  
W. Shyy
Keyword(s):  
Viscous Flow ◽  
Stokes Equations ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Hydraulic Turbine ◽  
Design Tool ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Alternative Designs

Viscous flow analysis based on the full Reynolds-averaged Navier-Stokes equations is being applied to successfully predict turbulent flow characteristics and energy losses in different hydraulic turbine components. It allows the designer to evaluate the hydraulic performance of alternative designs before proceeding with laboratory testing or to perform elaborate parametric study to optimize the hydraulic design. In this paper, the applications of three-dimensional viscous flow analysis as an analytical design tool for elbow draft tube and spiral casing are presented and their impact on engineering design assessed.

scholarly journals Development of Hybrid Airlift-Jet Pump with Its Performance Analysis

2018 ◽  
Vol 8 (9) ◽  
pp. 1413 ◽  
Author(s):  
Dan Yao ◽  
Kwongi Lee ◽  
Minho Ha ◽  
Cheolung Cheong ◽  
Inhiug Lee
Keyword(s):  
Boundary Conditions ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Stokes Equations ◽  
Flow Characteristics ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Jet Pump ◽  
Two Phase

A new pump, called the hybrid airlift-jet pump, is developed by reinforcing the advantages and minimizing the demerits of airlift and jet pumps. First, a basic design of the hybrid airlift-jet pump is schematically presented. Subsequently, its performance characteristics are numerically investigated by varying the operating conditions of the airlift and jet parts in the hybrid pump. The compressible unsteady Reynolds-averaged Navier-Stokes equations, combined with the homogeneous mixture model for multiphase flow, are used as the governing equations for the two-phase flow in the hybrid pump. The pressure-based methods combined with the Pressure-Implicit with Splitting of Operators (PISO) algorithm are used as the computational fluid dynamics techniques. The validity of the present numerical methods is confirmed by comparing the predicted mass flow rate with the measured ones. In total, 18 simulation cases that are designed to represent the various operating conditions of the hybrid pump are investigated: eight of these cases belong to the operating conditions of only the jet part with different air and water inlet boundary conditions, and the remaining ten cases belong to the operating conditions of both the airlift and jet parts with different air and water inlet boundary conditions. The mass flow rate and the efficiency are compared for each case. For further investigation into the detailed flow characteristics, the pressure and velocity distributions of the mixture in a primary pipe are compared. Furthermore, a periodic fluctuation of the water flow in the mass flow rate is found and analyzed. Our results show that the performance of the jet or airlift pump can be enhanced by combining the operating principles of two pumps into the hybrid airlift-jet pump, newly proposed in the present study.

Cascade viscous flow analysis using the Navier-Stokes equations

1987 ◽  
Vol 3 (5) ◽  
pp. 406-414 ◽  
Author(s):  
Roger L. Davis ◽  
Ron-Ho Ni ◽  
James E. Carter
Keyword(s):  
Viscous Flow ◽  
Stokes Equations ◽  
Flow Analysis ◽  
Navier Stokes ◽  
Navier Stokes Equations

Unsteady Flow Structure and Global Variables in a Centrifugal Pump

2006 ◽  
Vol 128 (5) ◽  
pp. 937-946 ◽  
Author(s):  
José González ◽  
Carlos Santolaria
Keyword(s):  
Unsteady Flow ◽  
Centrifugal Pump ◽  
Flow Structure ◽  
Flow Model ◽  
Stokes Equations ◽  
Flow Analysis ◽  
Operating Conditions ◽  
Local Flow ◽  
Global Variables ◽  
Wide Range

A relationship between the global variables and the dynamic flow structure numerically obtained for a low specific speed centrifugal pump is presented in this paper. A previously developed unsteady flow model is used to correlate the dynamic field with the flow characteristics inside the impeller and volute of a single-stage commercial pump. Actually, the viscous incompressible Navier-Stokes equations are solved within a 3D unsteady flow model. A sliding mesh technique is applied to take into account the impeller-volute interaction. After the numerical model has been successfully compared with the experimental data for the unsteady pressure fluctuations pattern in the volute shroud, a new step is proposed in order to correlate the observed effects with the flow structure inside the pump. In particular, the torque as a function of the relative position of the impeller blades is related to the blades loading, and the secondary flow in the volute is related to the different pressure patterns numerically obtained. Local flow analysis and qualitative study of the helicity in different volute sections is performed. The main goal of the study presented is the successful correlation of local and global parameters for the flow in a centrifugal pump. The pressure forces seem to be the main driven mechanism to establish the flow features both in the impeller and volute, for a wide range of operating conditions.

scholarly journals Numerical Investigation of Liquid–Liquid Mixing in Modified T Mixer with 3D Obstacles

2021 ◽  
pp. 25-32
Author(s):  
Md. Readul Mahmud
Keyword(s):  
Numerical Investigation ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Channel Length ◽  
Navier Stokes ◽  
Mixing Efficiency ◽  
Mixing Performance ◽  
Wide Range

The fluids inside passive micromixers are laminar in nature and mixing depends primarily on diffusion. Hence mixing efficiency is generally low, and requires a long channel length and longtime compare to active mixers. Various designs of complex channel structures with/without obstacles and three-dimensional geometries have been investigated in the past to obtain an efficient mixing in passive mixers. This work presents a design of a modified T mixer. To enhance the mixing performance, circular and hexagonal obstacles are introduced inside the modified T mixer. Numerical investigation on mixing and flow characteristics in microchannels is carried out using the computational fluid dynamics (CFD) software ANSYS 15. Mixing in the channels has been analyzed by using Navier–Stokes equations with water-water for a wide range of the Reynolds numbers from 1 to 500. The results show that the modified T mixer with circular obstacles has far better mixing performance than the modified T mixer without obstacles. The reason is that fluids' path length becomes longer due to the presence of obstacles which gives fluids more time to diffuse. For all cases, the modified T mixer with circular obstacle yields the best mixing efficiency (more than 60%) at all examined Reynolds numbers. It is also clear that efficiency increase with axial length. Efficiency can be simply improved by adding extra mixing units to provide adequate mixing. The value of the pressure drop is the lowest for the modified T mixer because there is no obstacle inside the channel. Modified T mixer and modified T mixer with circular obstacle have the lowest and highest mixing cost, respectively. Therefore, the current design of modified T with circular obstacles can act as an effective and simple passive mixing device for various micromixing applications.

Rarefied Gas Flow Analysis of a Suborbital Shuttle With the Academic CFD Code Galatea

2017 ◽  
Author(s):  
Angelos G. Klothakis ◽  
Georgios N. Lygidakis ◽  
Ioannis K. Nikolos
Keyword(s):  
Gas Flow ◽  
Microelectromechanical Systems ◽  
Stokes Equations ◽  
Rarefied Gas ◽  
Flow Analysis ◽  
Velocity Slip ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Rarefied Gas Flows ◽  
Wide Range

During the past decade considerable efforts have been exerted for the simulation of rarefied gas flows in a wide range of applications, like the flow over suborbital vehicles, in microelectromechanical systems, etc. Such flows appear to be significantly different from those at the continuum regime, making the Navier-Stokes equations to fail without further amendment. In this study an in-house academic CFD solver, named Galatea, is modified appropriately to account for rarefied gases. The no-slip condition on solid walls is no longer valid, hence, velocity slip and temperature jump boundary conditions are applied instead. Additionally, a second-order accurate slip model has been incorporated, namely, this of Beskok and Karniadakis, increasing the accuracy in the same area but avoiding simultaneously the numerical difficulties, entailed by the computation of the second derivative of slip velocity when complex geometries and unstructured grids are coupled. The proposed solver is validated against rarefied laminar flow over a suborbital shuttle, designed by the Azim’UTBM team. The obtained results are compared with those extracted with the parallel open-source kernel SPARTA, which is based on the DSMC method. A satisfactory agreement is reported between the two methodologies, demonstrating the potential of the modified solver to simulate effectively such flows.

scholarly journals Solution of Particulate Viscous Flow in a Radial Inflow Turbine

1983 ◽  
Author(s):  
B. V. R. Vittal ◽  
W. Tabakoff
Keyword(s):  
Stokes Equations ◽  
Continuous Phase ◽  
Solid Particles ◽  
Rotor Blades ◽  
Field Analysis ◽  
Numerical Code ◽  
Navier Stokes ◽  
Stream Channels ◽  
Carrier Fluid ◽  
Radial Inflow Turbine

The presence of solid particles in turbomachinery flow affects the component performance as well as its life. The subject of particulated flows can be broadly divided into three parts, namely, particle trajectories, the effect of particles on the aerodynamics of flow and material erosion. The first two aspects are investigated in this paper taking into account the viscosity of the carrier fluid. The Lagrangian formulation is adopted for the particles, whereas the Eulerian approach is used for the continuous phase. The effect of particles is incorporated as interphase force terms in the fully incompressible stream function-vorticity form of the Navier-Stokes equations. The field analysis is based on the numerical integration of this equation over the rotor blade to blade stream channels. The numerical code used to solve the governing equations employs a nonorthogonal boundary fitted coordinate system that suits the most complicated blade geometries. The trajectories of the solid particles are determined including particle impacts with the blades. The particle rebounding velocity and direction after each impact is determined using semi-empirical correlations for the restitution ratios obtained experimentally. The method of analysis is applied to a radial inflow turbine. The effect of particles on the aerodynamics of the flow is studied by analyzing the fluid streamline pattern in the rotor blades with and without solid particles. The analysis is carried out for various particle concentrations.

A Network Technique for Metal Flow Analysis in the Filling System of Pressure Diecasting and its Experimental Verification on a Cold Chamber Machine

1992 ◽  
Vol 206 (4) ◽  
pp. 261-275 ◽  
Author(s):  
S B Sulaiman ◽  
D T Gethin
Keyword(s):  
Stokes Equations ◽  
Metal Flow ◽  
Flow Analysis ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Part Type ◽  
Filling System ◽  
Cold Chamber ◽  
Actual Part

This study reports the results of analysis and measurement of metal flow in the pressure diecasting process. The analysis involved the simplification of the Navier Stokes equations and solution of the resulting set using a network method. Since the filling system is an important part of the pressure diecasting process, this aspect was, studied. Concurrently, an experiment to measure pressure in the diecasting process was carried out on a cold chamber machine to obtain the pressure history and flow characteristics. The predicted results were then compared with experimental data and agreement between them was achieved. In addition the fill of an actual part type has been carried out to illustrate the modelling capability.

A Study of the Viscous and Nonadiabatic Flow in Radial Turbines

1981 ◽  
Vol 103 (3) ◽  
pp. 481-489
Author(s):  
I. Khalil ◽  
W. Tabakoff
Keyword(s):  
Stokes Equations ◽  
Interaction Mechanism ◽  
Field Analysis ◽  
Numerical Code ◽  
Navier Stokes ◽  
Governing Equations ◽  
Stream Channels ◽  
Navier Stokes Equations ◽  
Separation Zones ◽  
Radial Turbines

A method for analyzing the viscous nonadiabatic flow within turbomachine rotors is presented. The field analysis is based upon the numerical integration of the incompressible Navier-Stokes equations together with the energy equation over the rotors blade-to-blade stream channels. The numerical code used to solve the governing equations employs a nonorthogonal boundary fitted coordinate system that suits the most complicated blade geometries. Effects of turbulence are modeled with two equations; one expressing the development of the turbulence kinetic energy and the other its dissipation rate. The method of analysis is applied to a radial inflow turbine. The solution obtained indicates the severity of the complex interaction mechanism that occurs between different flow regimes (i.e., boundary layers, recirculating eddies, separation zones, etc.). Comparison with nonviscous flow solutions tend to justify strongly the inadequacy of using the latter with standard boundary layer techniques to obtain viscous flow details within turbomachine rotors. Capabilities and limitations of the present method of analysis are discussed.

scholarly journals BLOOD FLOW ANALYSIS OF POLYURETHANE HEART VALVES AT PEAK SYSTOLE

2006 ◽  
Vol 18 (01) ◽  
pp. 13-18
Author(s):  
CHEUNG-HWA HSU
Keyword(s):  
Blood Flow ◽  
Heart Valves ◽  
Stokes Equations ◽  
Flow Analysis ◽  
Anticoagulation Therapy ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Maximum Flow ◽  
Navier Stokes ◽  
Hemodynamic Characteristics

Polyurethane (PU) heart valves provide central flow at peak systole and the associated hemodynamic characteristics are superior to that of mechanical valves with almost no anticoagulation therapy for patients. Durability performances, on the other hand, are also superior to those of biological valves. This paper analyzes blood flow characteristics of the PU heart valves at fully open position with computational fluid dynamics. These data provide information for the improvement of leaflets and leaflet support geometry to minimize the scale of recirculation zone of the flow field. To simulate the hemodynamic characteristics of the blood flow, CFX-4.3 software with the finite volume method is utilized to analyze the three-dimensional Reynolds-averaged Navier-Stokes equations. By modifying the geometry of leaflets along with the supports, the scale of vortex flow and blood velocity are reduced obviously. Maximum flow velocity reduces 33% compared to that of original model at peak systole.

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