scholarly journals VELOCITY FIELD IN A STEADY BREAKER

1980 ◽  
Vol 1 (17) ◽  
pp. 30
Author(s):  
J.A. Battjes ◽  
T. Sakai
Keyword(s):  
Experimental Investigation ◽  
Velocity Field ◽  
Flow Field ◽  
Turbulent Flow ◽  
Turbulent Wake ◽  
Laser Doppler ◽  
Reynolds Stresses ◽  
Doppler System ◽  
Steady Current ◽  
Turbulent Flow Field

An experimental investigation is described of the velocity field in a steady, spilling-type breaker, generated on a steady current by a submerged hydrofoil. Velocities have been measured with a laser-doppler system, and analysed with respect to mean and rms-values as well as Reynolds stresses. The results indicate that the turbulent flow field downstream of the initiation of the separation at the surface resembles that in a turbulent wake.

scholarly journals THE COMPUTATION OF BED SHEAR IN A NUMERICAL MODEL

1984 ◽  
Vol 1 (19) ◽  
pp. 114 ◽  
Author(s):  
W. Leeuwenstein ◽  
H.G. Wind
Keyword(s):  
Velocity Field ◽  
Flow Field ◽  
Turbulent Flow ◽  
Flow Model ◽  
Morphological Changes ◽  
Local Scour ◽  
Shear Stresses ◽  
Time Step ◽  
Turbulent Flow Field ◽  
Hydraulics Laboratory

Obstructions located in coastal and offshore waters usually disturb the natural flow pattern. This disturbed flow will, in general, cause local morphological changes in the position of the erodable boundary. Often these changes should not be allowed to exceed certain limits, for example, when local scour around an offshore construction may endanger foundations. Local morphological changes result from changes in the local sediment balance, brought about by the flow disturbance. In the present paper a mathematical model is described which gives the bottom shear stresses and the configuration of the seabed around an obstruction using a computation of the two dimensional turbulent flow field. The obstruction considered is a submarine pipeline laid uncovered on a seabed consisting of non-cohesive sediment. A research project on the local scour near submarine pipelines is being carried out at the Delft University of Technology. Part of the project is the application and extension of an advanced numerical flow model for scour development near pipelines on the seabed exposed to current action. This work is being carried out in cooperation with the Delft Hydraulics Laboratory. The code of the flow model has been developed in a joint venture between the Delft Hydraulics Laboratory and the Laboratoire National d"Hydraulique in France. The turbulent flow field is computed taking into account the influence of turbulence generated at the bed and by the pipe. The bed shear stresses are assumed to play the key role in the interaction between the flow and the seabed. In the computer model the bed shear is related to the flow through the "law of the wall". The model operation is schematized in the diagram below in which the first loop represents the evolution of the velocity field through a series of hydraulic time steps. After the velocity field is stabilized, in the second loop one morphological time step can be used for the computation of the local seabed changes. In this second loop the computed bed shear is applied together with a sediment transport formula. After the morphological time step a new bed topography is obtained and a new grid is generated for the next flow computation.

Turbulent flow field in a scour hole at a semicircular abutment

2005 ◽  
Vol 32 (1) ◽  
pp. 213-232 ◽  
Author(s):  
Subhasish Dey ◽  
Abdul Karim Barbhuiya
Keyword(s):  
Flow Field ◽  
Turbulent Flow ◽  
Three Dimensional ◽  
Shear Stresses ◽  
Reynolds Stresses ◽  
Primary Vortex ◽  
Scour Hole ◽  
Turbulent Flow Field ◽  
Development And Validation ◽  
Bed Shear Stresses

The three-dimensional turbulent flow field in a scour hole at a semicircular abutment under a clear water regime was experimentally measured in a laboratory flume using an acoustic Doppler velocimeter. The distributions of time-averaged velocity components, turbulent intensity components, turbulent kinetic energy, and Reynolds stresses at different azimuthal planes are presented. Upstream, presentation of flow field through vector plots at azimuthal and horizontal planes shows the existence of a large primary vortex associated with the downflow inside the scour hole. On the other hand, downstream, the flow field is irregular. The bed shear stresses are determined from the Reynolds stresses and velocity gradients. The data presented in this paper would be useful for the development and validation of flow field models, which can be used to determine the strength of the primary vortex that is used to estimate scour depth at bridge abutments.Key words: bridge abutments, fluid flow, three-dimensional flow, turbulent flow, open channel flow, scour, sediment transport, hydraulic engineering.

scholarly journals The Structure of a Turbulent Wake Behind a Cruciform Circular Cylinder : 2nd Report, The Streamwise Development of turbulent flow field

1983 ◽  
Vol 26 (214) ◽  
pp. 521-528 ◽  
Author(s):  
Hideo OSAKA ◽  
Hidemi YAMADA ◽  
Ikuo NAKAMURA ◽  
Yoshimasa KUWATA ◽  
Yoshiro KAGEYAMA
Keyword(s):  
Circular Cylinder ◽  
Flow Field ◽  
Turbulent Flow ◽  
Turbulent Wake ◽  
Turbulent Flow Field

Numerical simulations and analysis of the turbulent flow field in a practical gas turbine engine combustor

2021 ◽  
pp. 095765092110632
Author(s):  
Veeraraghava R Hasti ◽  
Prithwish Kundu ◽  
Sibendu Som ◽  
Jay P Gore
Keyword(s):  
Flow Field ◽  
Turbulent Flow ◽  
Numerical Simulations ◽  
Gas Turbine ◽  
Adaptive Mesh Refinement ◽  
Three Dimensional ◽  
Adaptive Mesh ◽  
Turbulent Structures ◽  
Cut Cell ◽  
Turbulent Flow Field

The turbulent flow field in a practical gas turbine combustor is very complex because of the interactions between various flows resulting from components like multiple types of swirlers, dilution holes, and liner effusion cooling holes. Numerical simulations of flows in such complex combustor configurations are challenging. The challenges result from (a) the complexities of the interfaces between multiple three-dimensional shear layers, (b) the need for proper treatment of a large number of tiny effusion holes with multiple angles, and (c) the requirements for fast turnaround times in support of engineering design optimization. Both the Reynolds averaged Navier–Stokes simulation (RANS) and the large eddy simulation (LES) for the practical combustor geometry are considered. An autonomous meshing using the cut-cell Cartesian method and adaptive mesh refinement (AMR) is demonstrated for the first time to simulate the flow in a practical combustor geometry. The numerical studies include a set of computations of flows under a prescribed pressure drop across the passage of interest and another set of computations with all passages open with a specified total flow rate at the plenum inlet and the pressure at the exit. For both sets, the results of the RANS and the LES flow computations agree with each other and with the corresponding measurements. The results from the high-resolution LES simulations are utilized to gain fundamental insights into the complex turbulent flow field by examining the profiles of the velocity, the vorticity, and the turbulent kinetic energy. The dynamics of the turbulent structures are well captured in the results of the LES simulations.

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