scholarly journals The influence of transverse slope effects on large scale morphology in morphodynamic models

2018 ◽  
Vol 40 ◽  
pp. 04021 ◽  
Author(s):  
Anne Baar ◽  
Marcio Boechat Albernaz ◽  
Wout van Dijk ◽  
Maarten Kleinhans
Keyword(s):  
Sediment Transport ◽  
Large Scale ◽  
Flow Direction ◽  
Main Flow ◽  
Scale Morphology ◽  
Channel Depth ◽  
Braiding Index ◽  
Main Flow Direction ◽  
Transverse Slope ◽  
Crucial Part

Large-scale morphology is greatly affected by the amount of downslope sediment transport on slopes transverse to the main flow direction, which determines bar length and bifurcation dynamics. Consequently, the transverse slope parameter is a crucial part of morphodynamic models. However, existing models have the tendency to overpredict channel depth and braiding index, and therefore slope effects are often increased when calibrating on existing morphology. The objective of this study is to identify possible causes of the overdeepening of channels in the morphodynamic model Delft3D, and to show how different slope effect parameterisations affect morphology in rivers and estuaries. Results show that the two methods to calculate transverse sediment transport in Delft3D have a significantly different effect on the predicted morphology and this effect is larger for environments with a large braiding index, in combination with the sediment transport predictor of Engelund-Hansen. Results furthermore imply that even when models are initially calibrated on existing morphology, results could significantly differ downstream when calibrated with a different choice of transverse slope option.

The meandering behaviour of large-scale structures in turbulent boundary layers

2019 ◽  
Vol 865 ◽  
Author(s):  
Kevin Kevin ◽  
Jason Monty ◽  
Nicholas Hutchins
Keyword(s):  
Boundary Layers ◽  
Large Scale ◽  
Flow Direction ◽  
Main Flow ◽  
Turbulent Structures ◽  
Velocity Fluctuations ◽  
Large Scale Structures ◽  
Main Flow Direction ◽  
Scale Structures ◽  
Spanwise Velocity

This paper quantifies the instantaneous form of large-scale turbulent structures in canonical smooth-wall boundary layers, demonstrating that they adhere to a form that is consistent with the self-sustaining streak instability model suggested by Flores & Jiménez (Phys. Fluids, vol. 22, 2010, 071704) and Hwang & Cossu (Phys. Fluids, vol. 23, 2011, 061702). Our motivation for this study stems from previous observations of large-scale streaks that have been spatially locked in position within spanwise-heterogeneous boundary layers. Here, using similar tools, we demonstrate that the randomly occurring large-scale structures in canonical layers show similar behaviour. Statistically, we show that the signature of large-scale coherent structures exhibits increasing meandering behaviour with distance from the wall. At the upper edge of the boundary layer, where these structures are severely misaligned from the main-flow direction, the induced velocities associated with the strongly yawed vortex packets/clusters yield a significant spanwise-velocity component leading to an apparent oblique coherence of spanwise-velocity fluctuations. This pronounced meandering behaviour also gives rise to a dominant streamwise periodicity at a wavelength of approximately $6\unicode[STIX]{x1D6FF}$. We further statistically show that the quasi-streamwise roll-modes formed adjacent to these very large wavy motions are often one-sided (spanwise asymmetric), in stark contrast to the counter-rotating form suggested by conventional conditionally averaged representations. To summarise, we sketch a representative picture of the typical large-scale structures based on the evidence gathered in this study.

Large Eddy Simulation of the 7-7-7 Shaped Film Cooling Hole at Axial and Compound Angle Orientations

2020 ◽  
Author(s):  
Kevin Tracy ◽  
Stephen P. Lynch
Keyword(s):  
Large Eddy Simulation ◽  
Film Cooling ◽  
Flow Direction ◽  
Main Flow ◽  
Blowing Ratio ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Cooling Hole ◽  
Main Flow Direction ◽  
Compound Angle

Abstract Shaped film cooling holes are used extensively for film cooling in gas turbines due to their superior performance in keeping coolant attached to the surface, relative to cylindrical holes. However, fewer studies have examined the impact of the orientation of the shaped hole axis relative to the main flow direction, known as a compound angle. A compound angle can occur intentionally due to manufacturing, or unintentionally due to changes in the main flow direction at off-design conditions. In either case, the compound angle causes the film cooling jet to roll up into a strong streamwise vortex that changes the lateral distribution of coolant, relative to the pair of vortices that develop from an axially oriented film cooling hole. In this study, Large Eddy Simulation (LES) using the Wall-Adapting Local Eddy Viscosity (WALE) model was performed on the publicly available 7-7-7 shaped film cooling hole, at two orientations (0°, 30°) and two blowing ratios (M = 1, 3). Laterally-averaged film effectiveness was largely unchanged by a compound angle at a blowing ratio of 1, but improved at a blowing ratio of 3. For both blowing ratios, the lateral distribution of film was more uniform with the addition of a 30° compound angle. Both wall normal and lateral turbulent convective heat transfer was increased by the addition of a compound angle at both blowing ratios.

Influence of Chord Length and Inlet Boundary Layer on the Secondary Losses of Turbine Blades

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Helmut Sauer ◽  
Robin Schmidt ◽  
Konrad Vogeler
Keyword(s):  
Boundary Layer ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Flow Direction ◽  
Velocity Ratio ◽  
Main Flow ◽  
Chord Length ◽  
Displacement Thickness ◽  
Wide Range ◽  
Main Flow Direction

In this paper, results concerning the influence of chord length and inlet boundary layer thickness on the endwall loss of a linear turbine cascade are discussed. The investigations were performed in a low speed cascade tunnel using the turbine profile T40. The turning of 90 deg and 70 deg, the velocity ratio in the cascade from 1.0 to 3.5 as well as the chord length of 100 mm, 200 mm, and 300 mm were specified. In a measurement distance of one chord behind the cascade in main flow direction, an approximate proportionality of endwall loss and chord was observed in a wide range of velocity ratios. At small measurement distances (e.g., s2/l=0.4), this proportionality does not exist. If a part of the flow path within the cascade is approximately incorporated, a proportionality to the chord at small measurement distances can be obtained, too. Then, the magnitude of the endwall loss mainly depends on the distance in main flow direction. At velocity ratios near 1.0, the influence of the chord decreases rapidly, while at a velocity ratio of 1.0, the endwall loss is independent of the chord. By varying the inlet boundary layer thickness, no correlation of displacement thickness and endwall loss was achieved. A calculation method according to the modified integral equation by van Driest delivers the wall shear stress. Its influence on the endwall loss was analyzed.

scholarly journals Three-Dimensional Couette Flow of a Second-Grade Fluid Along Periodic Injection/Suction

Coatings ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 553 ◽  
Author(s):  
Muhammad Afzal Rana ◽  
Yasar Ali ◽  
Babar Ahmad ◽  
Muhammad Touseef Afzal Rana
Keyword(s):  
Transverse Direction ◽  
Flow Direction ◽  
Three Dimensional ◽  
Analytic Solutions ◽  
Main Flow ◽  
Second Grade ◽  
Second Grade Fluid ◽  
Suction Velocity ◽  
Grade Fluid ◽  
Main Flow Direction

This work explores the three-dimensional laminar flow of an incompressible second-grade fluid between two parallel infinite plates. The assumed suction velocity comprises a basic steady dispersal with a superimposed weak transversally fluctuating distribution. Because of variation of suction velocity in transverse direction on the wall, the problem turns out to be three-dimensional. Analytic solutions for velocity field, pressure and skin friction are presented and effects of dimensionless parameters emerging in the model are discussed. It is observed that the non-Newtonian parameter plays dynamic part to rheostat the velocity component along main flow direction.

Experimental Flow Structure Analysis in Plates With 90° Chevron Geometry by a Particle Visualization Technique

2007 ◽  
Author(s):  
Jose M. Luna ◽  
Ricardo Romero-Mendez ◽  
Abel Hernandez-Guerrero ◽  
Jose C. Rubio-Arana
Keyword(s):  
Flow Direction ◽  
Main Flow ◽  
Flow Structures ◽  
Visualization Technique ◽  
Corrugated Surfaces ◽  
Wide Range ◽  
Main Flow Direction ◽  
Corrugated Plates ◽  
Visualization Experiments ◽  
Particle Visualization

The flow structures in the cavities of parallel cross-corrugated surfaces, also called chevron geometry, are investigated in this work using an experimental visualization method. An angle of 45° between the corrugations and the main flow direction has been considered. Reviews show that a considerable amount of investigations, mainly experimental, of heat transfer and pressure drop for cross-corrugated plates has been performed, whereas for the flow field in the cavities has only been investigated numerically. The flow visualization experiments are performed inside a water tunnel using a wide range of the hydraulic diameter-based Reynolds number.

Detached Eddy Simulation of Turbulent Flow and Heat Transfer in a Ribbed Duct

2005 ◽  
Vol 127 (5) ◽  
pp. 888-896 ◽  
Author(s):  
Aroon K. Viswanathan ◽  
Danesh K. Tafti
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Flow Direction ◽  
Main Flow ◽  
Detached Eddy Simulation ◽  
Heat Transfer Characteristics ◽  
Eddy Simulation ◽  
Flow And Heat Transfer ◽  
Main Flow Direction ◽  
Key Features

Detached Eddy Simulation (DES) of a hydrodynamic and thermally developed turbulent flow is presented for a stationary duct with square ribs aligned normal to the main flow direction. The rib height to channel hydraulic diameter (e∕Dh) is 0.1, the rib pitch to rib height (P∕e) is 10 and the calculations have been carried out for a bulk Reynolds number of 20,000. DES calculations are carried out on a 963 grid, a 643 grid, and a 483 grid to study the effect of grid resolution. Based on the agreement with earlier LES computations, the 643 grid is observed to be suitable for the DES computation. DES and RANS calculations carried out on the 643 grid are compared to LES calculations on 963∕1283 grids and experimental measurements. The flow and heat transfer characteristics for the DES cases compare well with the LES results and the experiments. The average friction and the augmentation ratios are consistent with experimental results, predicting values within 10% of the measured quantities, at a cost lower than the LES calculations. RANS fails to capture some key features of the flow.

scholarly journals Research on the silver in the world flowing into Qing Dynasty

2019 ◽  
Vol 1 (1) ◽  
pp. 26-28
Author(s):  
Jun Wei
Keyword(s):  
Foreign Trade ◽  
Qing Dynasty ◽  
Flow Direction ◽  
Main Flow ◽  
The Other ◽  
The Qing Dynasty ◽  
The World ◽  
Main Flow Direction

In the 80 years of foreign trade in the Qing Dynasty, the main flow direction of silver was from Spain and Britain to Qing Dynasty, which is one of the main contents; the other is the materials, process and variety design of the silver flowing into the Qing Dynasty.

Investigation of a High Aspect Ratio Rectangular Channel With High Blockage Ratio Round-Corner Ribs

2004 ◽  
Author(s):  
Christophe Diette ◽  
Tony Arts ◽  
Olivier Sgarzi ◽  
Emmanuel Laroche
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Large Scale ◽  
Flow Direction ◽  
Flow Behavior ◽  
Rectangular Channel ◽  
Internal Cooling ◽  
Liquid Crystal Thermography ◽  
Main Flow Direction

The flow behavior and heat transfer were measured in a large scale, high aspect ratio, turbine blade rib-roughened internal cooling channel. The ribs, installed on one wall, were inclined at 90 deg with respect to the main flow direction and generated a blockage of 20%. The rib corners were rounded to take into account manufacturing aspects. The bulk flow Reynolds number was 20,000. Pressure drop and velocity measurements were first conducted. Liquid crystal thermography was applied to quantify the heat transfer, not only along the ribbed and the smooth opposite walls but also on the rib itself. Numerical simulations were conducted with two flow solvers, IGG/FINE (Numeca) and MSD (ONERA) and compared with measurements. They also supported the analysis of the flow behavior. The influence of round-corner versus sharp edge ribs was numerically evaluated with IGG/FINE.

Movement of Cell Flowing Over Oblique Micro Grooves in Flow Channel

2021 ◽  
Author(s):  
Shigehiro Hashimoto ◽  
Hiroki Yonezawa
Keyword(s):  
Flow Direction ◽  
Longitudinal Axis ◽  
Flow Channel ◽  
Main Flow ◽  
Flow Test ◽  
Micro Flow ◽  
Main Flow Direction ◽  
Mouse Myoblast ◽  
Made In

Abstract A micro flow-channel with bottom-microgrooves has been manufactured by photolithography technique for cell sorting. The movement of each cell passing over microgrooves has been analyzed in relation to cell deformation and alignment in vitro. The flow path (height 0.05 mm × width 1 mm × length 25 mm) between the two transparent PDMS disks has rectangular microgrooves (4.5 μm deep, 0.2 mm long) on the bottom. Variations are made in groove widths (0.03 mm, 0.04 mm, and 0.05 mm). The angle between the flow direction and the longitudinal axis of the groove is 45 degrees. Myoblasts (C2C12: mouse myoblast line) were used in the flow test. The main flow velocity of the medium (0.02 mm/s < vx < 0.23 mm/s) was controlled by the pressure difference between the inlet and the outlet. The shape of each flowing cell was tracked in a movie recorded by a camera attached to the eyepiece of the microscope. Experimental results show that the movement perpendicular to the main flow direction in the micro-groove can distinguish cells in relation to smaller deformations and larger alignment changes.

Sign in / Sign up

Export Citation Format

Share Document