Channel-Confined Wake Structure Interactions Between Two Permeable Side-By-Side Bars of a Square Cross-Section

2021 ◽  
Author(s):  
Saqib Jamshed ◽  
Amit Dhiman
Keyword(s):  
Cross Section ◽  
Vortex Shedding ◽  
Pressure Coefficient ◽  
Flow Characteristics ◽  
Darcy Number ◽  
Drag Forces ◽  
Coefficient Distribution ◽  
Wake Patterns ◽  
Lower Permeability ◽  
The Impact

Abstract The current research focuses on the laminar flow through permeable side-by-side bars of a square cross-section in a channel-confined domain. Vorticity generation on the leeward sides of the permeable bodies further necessitates the study for a better understanding of underlying physics. Reynolds number Re and Darcy number Da are varied from 5 to 150 and 10-6 to 10-2, respectively, at transverse gap ratios s/d=2.5-10. In the perspective of periodic unsteady flow, critical Re for the onset of vortex shedding is analyzed. Streamlines, vorticity, pressure coefficient distribution, and velocity profiles are discussed to identify the wake patterns. In lower permeability level, vortex-shedding from the permeable square cylinders is observed either in synchronized anti-phase mode or a single large vortex street with a synchronized in-phase pattern in the near wake. A steady-state wake pattern symmetric and flocked towards the centerline is observed for all s/d at a higher permeability level regardless of Re. Wake patterns are not altered for Da=10-6-10-3; instead, prompt extermination of the two vortex streets downstream is observed at Da=10-3 as compared to Da=10-6. The impact of s/d, Re, and permeability on the drag is examined. A jump in the flow characteristics and drag forces is noticed at higher Re for the mid-range Da remarkably at lower s/d. For the extent of high permeability, the drag coefficient asymptotically gets closer to zero.

Influence of a Finite Width Micro-Tab on the Spanwise Lift Distribution

2013 ◽  
Author(s):  
D. Holst ◽  
A. B. Bach ◽  
C. N. Nayeri ◽  
C. O. Paschereit
Keyword(s):  
Pressure Coefficient ◽  
Reynolds Numbers ◽  
Global Changes ◽  
Finite Width ◽  
Local Pressure ◽  
Low Reynolds Numbers ◽  
Pressure Distributions ◽  
Coefficient Distribution ◽  
Stereo Particle Image Velocimetry ◽  
The Impact

The results of surface pressure measurements are presented in this paper to gain further insight into the lift changing influence of finite width micro-tabs, especially in adjacent airfoil sections. Micro-tabs are a promising concept for load control on wind turbines. Local pressure distributions were measured in several rows of pressure taps in the vicinity of the finite width micro-tab attached to a FX 63-137 profile at low Reynolds numbers. The investigation focuses on length dependency, chordwise position, and interaction between two micro-tabs. Additionally, stereo Particle-Image-Velocimetry measurements were conducted to study the structure, sense of rotation, and influence of tab-induced tip vortices, as well as the impact of a finite width micro-tab on the model’s near wake. Experiments reveal relative changes of more than 30 % in the pressure coefficient distribution upstream of several micro-tab configurations. Furthermore, increments of 20 % are recorded in neighbouring sections not directly controlled by micro-tabs. Even higher changes are obtained in the region between two tabs. These improvements are attained due to local and global changes in the effective camber.

scholarly journals Load model for designing flexible steel barriers for debris flow mitigation

2019 ◽  
Vol 56 (6) ◽  
pp. 893-910 ◽  
Author(s):  
Corinna Wendeler ◽  
Axel Volkwein ◽  
Brian W. McArdell ◽  
Perry Bartelt
Keyword(s):  
Debris Flow ◽  
Pressure Coefficient ◽  
Flow Characteristics ◽  
Field Tests ◽  
Load Model ◽  
Dynamic Part ◽  
Pass Through ◽  
Run Up ◽  
Water Saturated ◽  
The Impact

Light-weight flexible steel net barriers catch coarse debris, but let some of the fine material and water pass through the net. They are difficult to design so that they can withstand the impact pressures of both boulder-laden granular and water-saturated debris flows. Using results from laboratory and full-scale field tests, a debris flow load model has been developed for flexible barriers in torrent channels. The model accounts for the forces of initial impact as well as the filling process discretized stepwise over time (barriers in the field and laboratory fill continuously). Laboratory tests with fast debris flow front velocities revealed a run-up behaviour that was not observed in the field (“pile-up”). The load model divides the flow forces into a hydrostatic component and a dynamic part depending on a pressure coefficient, the flow velocity, and the density of the flow. This dynamic part, which is more complex to quantify, accounts for the wide-ranging debris flow characteristics from watery and muddy debris floods to granular friction-dominated mass flows.

scholarly journals Technical Note: Flow velocity and discharge measurement in rivers using terrestrial and unmanned-aerial-vehicle imagery

2020 ◽  
Vol 24 (3) ◽  
pp. 1429-1445 ◽  
Author(s):  
Anette Eltner ◽  
Hannes Sardemann ◽  
Jens Grundmann
Keyword(s):  
Flow Velocity ◽  
Unmanned Aerial Vehicle ◽  
Cross Section ◽  
Flow Characteristics ◽  
Technical Note ◽  
Surface Flow ◽  
Contactless Measurement ◽  
Aerial Vehicle ◽  
The Impact ◽  
Flow Velocities

Abstract. An automatic workflow to measure surface flow velocities in rivers is introduced, including a Python tool. The method is based on particle-tracking velocimetry (PTV) and comprises an automatic definition of the search area for particles to track. Tracking is performed in the original images. Only the final tracks are geo-referenced, intersecting the image observations with water surface in object space. Detected particles and corresponding feature tracks are filtered considering particle and flow characteristics to mitigate the impact of sun glare and outliers. The method can be applied to different perspectives, including terrestrial and aerial (i.e. unmanned-aerial-vehicle; UAV) imagery. To account for camera movements images can be co-registered in an automatic approach. In addition to velocity estimates, discharge is calculated using the surface velocities and wetted cross section derived from surface models computed with structure-from-motion (SfM) and multi-media photogrammetry. The workflow is tested at two river reaches (paved and natural) in Germany. Reference data are provided by acoustic Doppler current profiler (ADCP) measurements. At the paved river reach, the highest deviations of flow velocity and discharge reach 4 % and 5 %, respectively. At the natural river highest deviations are larger (up to 31 %) due to the irregular cross-section shapes hindering the accurate contrasting of ADCP- and image-based results. The provided tool enables the measurement of surface flow velocities independently of the perspective from which images are acquired. With the contactless measurement, spatially distributed velocity fields can be estimated and river discharge in previously ungauged and unmeasured regions can be calculated, solely requiring some scaling information.

The Effect of Mach Number on the Loss Generation of LP Turbines

2012 ◽  
Author(s):  
Raúl Vázquez ◽  
Diego Torre
Keyword(s):  
Mach Number ◽  
Total Pressure ◽  
High Speed ◽  
State Of The Art ◽  
Pressure Coefficient ◽  
Airfoil Surface ◽  
High Lift ◽  
Pressure Losses ◽  
Coefficient Distribution ◽  
The Impact

The effect of Mach number on the loss generation of Low Pressure (LP) Turbines has been investigated experimentally in a pair of turbine high-speed rigs. Both rigs consist of a rotor-stator configuration. All the airfoils are high lift, high aspect ratio and high turning blades that are characteristic of state of the art LP Turbines. Both rigs are identical with exception of the stator. Two sets of stators have been manufactured and tested. The aerodynamic shape of both stators have been designed in order to achieve the same spanwise distribution of Cp (Compressible Pressure coefficient) over the airfoil surface, each one to its corresponding design Mach number (0.61 and 0.88 respectively). The aim of this experiment is to obtain the sensitivity of profile and endwall losses to Mach number by means of a back-to-back comparison between both sets of airfoils. Because the two sets of stators maintain the same pressure coefficient distribution, Reynolds number and velocity triangles, each one to its corresponding design Mach number; one can state that the results are only affected by the compressibility. Experimental results are presented and compared in terms of area average, radial pitchwise average distributions and exit plane contours of total pressure losses. To complete the paper, the impact of the results on the design of LP Turbines is discussed and presented.

Turbine Blade Trailing Edge Flow Characteristics at High Subsonic Outlet Mach Number

2003 ◽  
Vol 125 (2) ◽  
pp. 298-309 ◽  
Author(s):  
Claus H. Sieverding ◽  
Hugues Richard ◽  
Jean-Michel Desse
Keyword(s):  
Mach Number ◽  
Pressure Distribution ◽  
Turbine Blade ◽  
Vortex Shedding ◽  
High Speed ◽  
Pressure Coefficient ◽  
Vortex Formation ◽  
Flow Characteristics ◽  
Suction Side ◽  
Trailing Edge

The paper presents an experimental investigationof the effect of the trailing edge vortex shedding on the steady and unsteady trailing blade pressure distribution of a turbine blade at high subsonic Mach number M2,is=0.79 and high Reynolds number RE=2.8×106. The vortex formation and shedding process is visualized using a high-speed schlieren camera and a holographic interferometric density measuring technique. The blade is equipped with a rotatable trailing edge cylinder instrumented side-by-side with a pneumatic pressure tap and a fast response pressure sensor for detailed measurements of the trailing edge pressure distribution. The experiments demonstrate that contrary to the isobaric dead air region demonstrated at low subsonic Mach numbers the data reveal the existence of a highly nonuniform trailing edge pressure distribution with a strong pressure minimum at the center of the trailing edge. This finding is significant for the determination of the base pressure coefficient that is in general measured with a single pressure-sensing hole at the trailing edge center. The paper investigates further the effect of the vortex shedding on the blade rear suction side and discusses the superposition of unsteady effects emanating from the trailing edge and from the neighboring blade. The experimental data are a unique source for the validation of unsteady Navier-Stokes codes.

scholarly journals Flow velocity and discharge measurement in rivers using terrestrial and UAV imagery

2019 ◽  
Author(s):  
Anette Eltner ◽  
Hannes Sardemann ◽  
Jens Grundmann
Keyword(s):  
Flow Velocity ◽  
Cross Section ◽  
Flow Characteristics ◽  
Surface Flow ◽  
Spatially Distributed ◽  
Adcp Measurements ◽  
River Reach ◽  
Definition Of ◽  
The Impact ◽  
Flow Velocities

Abstract. An automatic workflow to measure surface flow velocities in rivers is introduced, including a Python tool. The method is based on PTV and comprises an automatic definition of the search area for particles to track. Tracking is performed in the original images. Only the final tracks are geo-referenced, intersecting the image observations with water surface in object space. Detected particles and corresponding feature tracks are filtered considering particle and flow characteristics to mitigate the impact of sun glare and outliers. The method can be applied to different perspectives, including terrestrial and aerial (i.e. UAV) imagery. To account for camera movements images can be co-registered in an automatic approach. In addition to velocity estimates, discharge is calculated using the surface velocities and wetted cross-section derived from surface models computed with structure-from-motion and multi-media photogrammetry. The workflow is tested at two river reaches (paved and natural) in Germany. Reference data is provided by ADCP measurements. At the paved river reach highest deviations of flow velocity and discharge reach 5 % and 4 %, respectively. At the natural river deviations are larger (up to 31 %) due to the irregular cross-section shapes hindering accurate contrasting of ADCP- and image-based results. The provided tool enables the measurement of surface flow velocities independently of the perspective from which images are acquired. With the contact-less measurement spatially distributed velocity fields can be estimated and river discharge in previously ungauged and unmeasured regions can be calculated.

Effects of Transport Medium Composition on in vitro Drug Permeation across Excised Pig Intestinal Tissue

2020 ◽  
Vol 10 ◽  
Author(s):  
Bianca Peterson ◽  
Henrico Heystek ◽  
Josias H. Hamman ◽  
Johan D. Steyn
Keyword(s):  
Medium Composition ◽  
Screening Tests ◽  
Intestinal Tissue ◽  
Predictive Values ◽  
Transport Medium ◽  
Intestinal Fluids ◽  
Lower Permeability ◽  
The Impact ◽  
Simulated Intestinal Fluids

Background:: Knowledge of the permeation characteristics of new chemical entities across biological membranes is essential to drug research and development. Transport medium composition may affect the absorption of compounds during in vitro drug transport testing. To preserve the predictive values of screening tests, the possible influence of transport media on the solubility of model drugs, and on the activities of tight junctions and efflux transporter proteins (e.g. P-glycoprotein) must be known. Objective:: The aim of this study was to compare the impact of different transport media on the bi-directional transport of standard compounds, selected from the four classes of the Biopharmaceutical Classification System (BCS), across excised pig intestinal tissue. Methods:: The Sweetana-Grass diffusion apparatus was used for the transport studies. Krebs-Ringer bicarbonate (KRB) buffer and simulated intestinal fluids in the fed (FeSSIF) and fasted (FaSSIF) states were used as the three transport media, while the chosen compounds were abacavir (BCS class 1), dapsone (BCS class 2), lamivudine (BCS class 3) and furosemide (BCS class 4). Results:: Abacavir exhibited lower permeability in both the simulated intestinal fluids than in the KRB buffer. Dapsone showed similar permeability in all media. Lamivudine exhibited lower permeability in FaSSIF than in the other two media. Furosemide exhibited improved transport with pronounced efflux in FaSSIF. Conclusion:: Different permeation behaviors were observed for the selected drugs in the respective media, which may have resulted from their different physico-chemical properties, as well as from the effects that dissimilar transport media components had on excised pig intestinal tissue.

An improved de Laval nozzle experiment

2021 ◽  
pp. 030641902110341
Author(s):  
Nicholas Goodman ◽  
Brian J Leege ◽  
Peter E Johnson
Keyword(s):  
Data Acquisition ◽  
Laval Nozzle ◽  
Flow Characteristics ◽  
Data Acquisition System ◽  
Isentropic Flow ◽  
Hands On ◽  
De Laval Nozzle ◽  
Physical Phenomena ◽  
The Impact ◽  
The Relationship

Exposing students to hands-on experiments has been a common approach to illustrating complex physical phenomena that have been otherwise modelled solely mathematically. Compressible, isentropic flow in a duct is an example of such a phenomenon, and it is often demonstrated via a de Laval nozzle experiment. We have improved an existing converging/diverging nozzle experiment so that students can modify the location of the normal shock that develops in the diverging portion to better understand the relationship between the shock and the pressure. We have also improved the data acquisition system for this experiment and explained how visualisation of the standing shock is now possible. The results of the updated system demonstrate that the accuracy of the isentropic flow characteristics has not been lost. Through pre- and post-laboratory quizzes, we show the impact on student learning as well.

scholarly journals Charged current Drell-Yan production at N3LO

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
Claude Duhr ◽  
Falko Dulat ◽  
Bernhard Mistlberger
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Production Cross Section ◽  
Production Cross ◽  
Hadron Collider ◽  
Charge Asymmetry ◽  
Charged Current ◽  
Leading Order ◽  
Neutrino Pair ◽  
The Impact

Abstract We present the production cross section for a lepton-neutrino pair at the Large Hadron Collider computed at next-to-next-to-next-to-leading order (N3LO) in QCD perturbation theory. We compute the partonic coefficient functions of a virtual W± boson at this order. We then use these analytic functions to study the progression of the perturbative series in different observables. In particular, we investigate the impact of the newly obtained corrections on the inclusive production cross section of W± bosons, as well as on the ratios of the production cross sections for W+, W− and/or a virtual photon. Finally, we present N3LO predictions for the charge asymmetry at the LHC.

The flow characteristics around bridge piers under the impact of a ship

2020 ◽  
Vol 32 (6) ◽  
pp. 1165-1177
Author(s):  
Yan-fen Geng ◽  
Hua-qiang Guo ◽  
Xing Ke
Keyword(s):  
Flow Characteristics ◽  
Bridge Piers ◽  
The Impact
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