scholarly journals Studies on Driftwood Motions around Obstacles by Laboratory and Nnumerical Experiments

2018 ◽  
Vol 40 ◽  
pp. 02032 ◽  
Author(s):  
Ichiro Kimura ◽  
Kazuya Kitazono
Keyword(s):  
Numerical Model ◽  
Richardson Number ◽  
Flow Model ◽  
Three Dimensional ◽  
Point Of View ◽  
Type Model ◽  
Three Dimensional Flow ◽  
Governing Parameter ◽  
Secondary Current ◽  
Dimension Type

From the engineering point of view, prediction of driftwood motions around hydraulic obstacles in rivers is important. We carried out laboratory experiments to understand the driftwood behaviour around grid like obstacles and found out that there are two different patterns of the capturing process of driftwood: 2D (two-dimension) type and 3D (threedimensional) type. We proposed the governing parameter "Driftwood Richardson Number" for classifying the types of the driftwood capture. A numerical model to simulate driftwood motions based on the coupling of a Euler type three-dimensional flow model and a Lagrange type twodimensional driftwood model (3D-2D model) is proposed to analyse the driftwood behaviour around obstacles. The numerical model could predict well the flowing pattern of driftwood affected by the secondary current of the first kind in a meandering open channel. The numerical results with obstacles showed that the present 3D-2D type model is applicable only if the driftwood Richardson number is larger than 10, in which the driftwood capturing takes place in the 2D type.

Numerical Analysis of the Deterministic Stresses Associated to Impeller-Tongue Interactions in a Single Volute Centrifugal Pump

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
J. M. Fernández Oro ◽  
J. González ◽  
R. Barrio Perotti ◽  
M. Galdo Vega
Keyword(s):  
Numerical Analysis ◽  
Numerical Model ◽  
Centrifugal Pump ◽  
Turbulence Intensity ◽  
Three Dimensional ◽  
Relevant Information ◽  
Three Dimensional Flow ◽  
Deterministic Analysis ◽  
Starting Point ◽  
Flow Features

In this paper, a deterministic stress decomposition is applied over the numerical three-dimensional flow solution available for a single volute centrifugal pump. The numerical model has proven in previous publications its robustness to obtain the impeller to volute-tongue flow interaction, and it is now used as starting point for the current research. The main objective has been oriented toward a detailed analysis of the lack of uniformity in the flow that the volute tongue promotes on the blade-to-blade axisymmetric pattern. Through this analysis, the fluctuation field may be retrieved and main interaction sources have been pinpointed. The results obtained with the deterministic analysis become of paramount interest to understand the different flow features found in a typical centrifugal pump as a function of the flow rate. Moreover, this postprocessing tool provides an economic and easy procedure for designers to compare the different deterministic terms, also giving relevant information on the unresolved turbulence intensity scales. Complementarily, a way to model the turbulent effects in a systematic way is also presented, comparing their impact on the performance with respect to deterministic sources in a useful framework, that may be applied for similar kinds of pumps.

Excess Streamwise Vorticity and Its Role in Secondary Flow

1987 ◽  
Vol 201 (6) ◽  
pp. 413-420 ◽  
Author(s):  
P W James
Keyword(s):  
Secondary Flow ◽  
Gas Turbines ◽  
Three Dimensional ◽  
Point Of View ◽  
Streamwise Vorticity ◽  
Three Dimensional Flow ◽  
Approximate Methods ◽  
Blade Row ◽  
Flow Through ◽  
Loss Term

The purpose of this paper is, firstly, to show how the concept of excess secondary vorticity arises naturally from attempts to recover three-dimensional flow details lost in passage-averaging the equations governing the flow through gas turbines. An equation for the growth of excess streamwise vorticity is then derived. This equation, which allows for streamwise entropy gradients through a prescribed loss term, could be integrated numerically through a blade-row to provide the excess vorticity at the exit to a blade-row. The second part of the paper concentrates on the approximate methods of Smith (1) and Came and Marsh (2) for estimating this quantity and demonstrates their relationship to each other and to the concept of excess streamwise vorticity. Finally the relevance of the results to the design of blading for gas turbines, from the point of view of secondary flow, is discussed.

Turbulent Mixing With Density Differences

2011 ◽  
Author(s):  
Jos Derksen
Keyword(s):  
Turbulent Mixing ◽  
Richardson Number ◽  
Kinematic Viscosity ◽  
Three Dimensional ◽  
Flow Regimes ◽  
Reynolds Numbers ◽  
Flow Structures ◽  
Three Dimensional Flow ◽  
Flow Equations ◽  
Miscible Liquids

Homogenization of initially segregated and stably stratified systems consisting of two miscible liquids with different density and the same kinematic viscosity in an agitated tank was studied computationally. Reynolds numbers were in the range of 3,000 to 12,000 so that it was possible to solve the flow equations without explicitly modeling turbulence. The Richardson number that characterizes buoyancy was varied between 0 and 1. The stratification clearly lengthens the homogenization process. Two flow regimes could be identified. At low Richardson numbers large, three-dimensional flow structures dominate mixing, as is the case in non-buoyant systems. At high Richardson numbers the interface between the two liquids largely stays intact. It rises due to turbulent erosion, gradually drawing down and mixing up the lighter liquid.

Analysis of the Full Flow Field of Torque Converter

2012 ◽  
Vol 468-471 ◽  
pp. 674-677 ◽  
Author(s):  
Yu Long Lei ◽  
Chang Wang ◽  
Zheng Jie Liu ◽  
Xing Zhong Li
Keyword(s):  
Flow Field ◽  
Boundary Conditions ◽  
Flow Rate ◽  
Flow Model ◽  
Three Dimensional ◽  
Calculated Data ◽  
Torque Converter ◽  
Three Dimensional Flow ◽  
Sliding Mesh ◽  
Mesh Method

Establish the full three-dimensional flow model of the torque converter, proper mesh the model, select the appropriate boundary conditions, and use the sliding mesh method to deal with the interactions of the impeller, turbine, and reactor in different rotation speeds. Analysis the flow rate, pressure, and the loss of full flow field passage of the torque converter, elaborate the formation mechanism of the flow field, agreement with the experimental date compare to the calculated data, more accurate than the traditional single passage model compare to the full passage model, provide the direction of design optimization of the torque converter.

The Fan Blade Velocity Field Analysis of Scenery Tower Power Generation Device Based on FLUENT

2012 ◽  
Vol 512-515 ◽  
pp. 665-668
Author(s):  
Shu Jiang Li ◽  
Wen Juan Bai ◽  
Wei Min Yang
Keyword(s):  
Flow Model ◽  
Three Dimensional ◽  
Field Analysis ◽  
Distribution Area ◽  
Three Dimensional Flow ◽  
Wind Energy Conversion ◽  
The Common ◽  
Power Generation Device ◽  
Fan Blade ◽  
Common Function

Based on field theory and air dynamics theory, two kinds of different curvature blade rotation of velocity and its distribution area were simulated, through the establishment of the three-dimensional flow model for the scenery tower fan blade generator and the adoption of RNGK-epsilon turbulence model. Then reach a conclusion from comparison: Smaller curvature leaf has a higher wind speed than the bigger one, which is easy to wind energy conversion under the common function of the force in the rotating area.

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