scholarly journals Design, Construction and Evaluation of an Oscillating Vane Gust Generator for Atmospheric Flow Simulation

Wind ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 63-76
Author(s):  
Aaron French ◽  
Wilhelm Friess ◽  
Andrew Goupee ◽  
Keith Berube
Keyword(s):  
Test Section ◽  
Flow Simulation ◽  
Layer Growth ◽  
Wind Tunnels ◽  
Maximum Speed ◽  
Atmospheric Flow ◽  
Freestream Velocity ◽  
Section Size ◽  
Naca0018 Airfoil ◽  
Oscillation Frequencies

The study of unsteady aerodynamic phenomena in wind tunnels is supported by gust-generating devices capable of generating adjustable magnitude and periodicity velocity fluctuations in a flowfield. Gusts are typically generated actively by introducing moving vanes to direct the flow, or passively by tailoring the boundary layer growth and shape in the tunnel. The flow facility used here is a student-built closed-return low-speed wind tunnel, with a test section size of 750 mm × 750 mm and a maximum speed of 25 m/s. A two-vane gust generator utilizing NACA0018 airfoil sections of 150 mm chord length was designed and installed upstream of the test section. The flowfield was mapped with the installed vanes with and without gust actuation, utilizing a hot wire system. The tunnel with gust vanes exhibits a spatially uniform baseline turbulence intensity of 5%, with a steady state velocity deficit of 1 m/s in the vane–wake region. Upon introducing the gusting conditions at vane deflection angles of up to ±45°, velocity differences of up to 4 m/s were attained at 18 m/s freestream velocity at oscillation frequencies ranging between 1 Hz and 2 Hz.

Characterization of the Custom-Designed, High Reynolds Number Water Tunnel

2016 ◽  
Author(s):  
Yasaman Farsiani ◽  
Brian R. Elbing
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Test Section ◽  
High Reynolds Number ◽  
Layer Growth ◽  
Water Tunnel ◽  
Freestream Velocity ◽  
Section Design ◽  
High Reynolds

This paper reports on the characterization of the custom-designed high-Reynolds number recirculating water tunnel located at Oklahoma State University. The characterization includes the verification of the test section design, pump calibration and the velocity distribution within the test section. This includes an assessment of the boundary layer growth within the test section. The tunnel was designed to achieve a downstream distance based Reynolds number of 10 million, provide optical access for flow visualization and minimize inlet flow non-uniformity. The test section is 1 m long with 15.2 cm (6-inch) square cross section and acrylic walls to allow direct line of sight at the tunnel walls. The verification of the test section design was accomplished by comparing the flow quality at different location downstream of the flow inlet. The pump was calibrated with the freestream velocity with three pump frequencies and velocity profiles were measured at defined locations for three pump speeds. Boundary layer thicknesses were measured from velocity profile results and compared with analytical calculations. These measurements were also compared against the facility design calculations.

Comparison of LBM and FVM in the estimation of LAD stenosis

2021 ◽  
pp. 095441192110169
Author(s):  
Jian Liu ◽  
Yong Yu ◽  
Chenqi Zhu ◽  
Yu Zhang
Keyword(s):  
Stokes Equations ◽  
Flow Simulation ◽  
Diagnostic Methods ◽  
Computational Time ◽  
Speed Ratio ◽  
Maximum Speed ◽  
Fractional Flow ◽  
Local Flow ◽  
Non Invasive ◽  
Flow Reserve

The finite volume method (FVM)-based computational fluid dynamics (CFD) technology has been applied in the non-invasive diagnosis of coronary artery stenosis. Nonetheless, FVM is a time-consuming process. In addition to FVM, the lattice Boltzmann method (LBM) is used in fluid flow simulation. Unlike FVM solving the Navier–Stokes equations, LBM directly solves the simplified Boltzmann equation, thus saving computational time. In this study, 12 patients with left anterior descending (LAD) stenosis, diagnosed by CTA, are analysed using FVM and LBM. The velocities, pressures, and wall shear stress (WSS) predicted using FVM and LBM for each patient is compared. In particular, the ratio of the average and maximum speed at the stenotic part characterising the degree of stenosis is compared. Finally, the golden standard of LAD stenosis, invasive fractional flow reserve (FFR), is applied to justify the simulation results. Our results show that LBM and FVM are consistent in blood flow simulation. In the region with a high degree of stenosis, the local flow patterns in those two solvers are slightly different, resulting in minor differences in local WSS estimation and blood speed ratio estimation. Notably, these differences do not result in an inconsistent estimation. Comparison with invasive FFR shows that, in most cases, the non-invasive diagnosis is consistent with FFR measurements. However, in some cases, the non-invasive diagnosis either underestimates or overestimates the degree of stenosis. This deviation is caused by the difference between physiological and simulation conditions that remains the biggest challenge faced by all CFD-based non-invasive diagnostic methods.

Testing and Analysis of an Oscillating Hydrofoils Turbine Concept

2010 ◽  
Author(s):  
Thomas Kinsey ◽  
Guy Dumas
Keyword(s):  
Water Flow ◽  
Spatial Configuration ◽  
Flow Simulation ◽  
Rotor Blades ◽  
Electric Generator ◽  
Power Extraction ◽  
Reduced Frequency ◽  
Custom Made ◽  
2D Flow ◽  
Oscillation Frequencies

A new concept of hydrokinetic turbine using oscillating hydrofoils to extract energy from water currents (tidal or gravitational) is presented, tested and analyzed in the present investigation. Due to its rectangular extraction plane, this technology is particularly well suited for river beds and shallow waters near the coasts. The present turbine is a 2 kW prototype, composed of two rectangular oscillating hydrofoils of aspect ratio 7 in a tandem spatial configuration. The pitching motion of each hydrofoil is coupled to their cyclic heaving motion through four-link mechanisms which effectively yield a one-degree-of-freedom system driving a speed-controlled electric generator. The turbine has been mounted on a custom-made pontoon boat and dragged on a lake at different velocities. Instantaneous extracted power has been measured and cycle-averaged for several water flow velocities and hydrofoil oscillation frequencies. Results are demonstrated to be self-consistent and validate our extensive 2D flow simulation database. The present data show optimal performances of the oscillating hydrofoils concept at a reduced frequency of about 0.12, at which condition the measured power extraction efficiency reaches 40% once the overall losses in the mechanical system are taken into account. Further measurements of power extraction with a single oscillating hydrofoil have also been performed by taking out the downstream hydrofoil of the tandem pair. Those measurements favorably compare, quantitatively, with available 3D CFD predictions. The 40% hydrodynamic efficiency of this first prototype exceeds expectation and reaches levels comparable to the best performances achievable with modern rotor-blades turbines. It thus demonstrates the promising potential of the oscillating hydrofoils technology to efficiently extract power from an incoming water flow.

Videogrammetric Techniques for Wind Tunnel Testing and Applications

2014 ◽  
Vol 986-987 ◽  
pp. 1629-1633
Author(s):  
Zheng Yu Zhang ◽  
Xu Hui Huang ◽  
Jiang Yin ◽  
Han Xuan Lai
Keyword(s):  
Wind Tunnel ◽  
Wave Front ◽  
High Speed ◽  
Marked Point ◽  
Wind Tunnel Test ◽  
Wind Tunnels ◽  
Test Model ◽  
Wind Tunnel Testing ◽  
Section Size ◽  
Key Techniques

Videogrammetric measurement is a research focus for the organizations of wind tunnel test because of its no special requirements on the test model, its key techniques for the vibration environment of the high speed wind tunnel are introduced by this paper, such as the solution of exterior parameters with big-angle large overlap, the algorithm of image processing for extracting marked point, the method of camera calibration and wave-front distortion field measurement. The great requirements and application prospects of videogrammetry in wind tunnel fine testing have been demonstrated by several practice experiments, including to measure test model’s angle of attack, dynamic deformations and wave-front distortion field in high speed wind tunnels whose test section size is 2 meters.

Nuclear Blast Response of Airbreathing Propulsion Systems: Laboratory Measurements With an Operational J-85-5 Turbojet Engine

1982 ◽  
Vol 104 (3) ◽  
pp. 624-632 ◽  
Author(s):  
M. G. Dunn ◽  
J. M. Rafferty
Keyword(s):  
Frequency Response ◽  
Blast Wave ◽  
Test Section ◽  
Maximum Speed ◽  
Laboratory Measurements ◽  
Propulsion Systems ◽  
Pressure Transducers ◽  
Ludwieg Tube ◽  
Turbojet Engine ◽  
Blast Response

This paper describes an experimental technique that has been developed for the performance of controlled laboratory measurements of the nuclear blast response of airbreathing propulsion systems. The experiments utilize an available G.E. J-85-5 turbojet engine located in the test section of the Calspan Ludwieg-tube facility. Significant modifications, described herein, were made to this facility in order to adapt it to the desired configuration. The J-85 engine had previously been used at Calspan for other purposes and thus came equipped with eight pressure transducers at four axial locations along the compressor section. These transducers have a frequency response on the order of 40 KHz. Pressure histories obtained at several circumferential and axial locations along the compressor are presented for blast-wave equivalent overpressures up to 17.2 kPa (2.5 psi) at corrected engine speeds on the order of 94 percent of maximum speed.

Design, Characterization, and Verification of a Closed Loop Wind Tunnel With Linear Cascade and Upstream Wake Generator

2015 ◽  
Author(s):  
Carlos R. Gonzalez ◽  
Guillaume F. Bidan ◽  
Jason W. Bitting ◽  
Christopher M. Foreman ◽  
Jean-Philippe Junca-Laplace ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Test Section ◽  
Film Cooling ◽  
Spectral Characteristics ◽  
Test Facility ◽  
Flat Plates ◽  
Freestream Velocity ◽  
Linear Cascade ◽  
Wide Range ◽  
Stationary Frame

A new cascade wind tunnel has been designed and constructed at the LSU Wind Tunnel Laboratory. The objective was to develop a versatile test facility, suitable for a wide range of experimental studies and measurements on turbine airfoils, especially with regards to film-cooling incorporating realistic unsteady effects due to passing wakes. The test section consists of a four passage linear cascade composed of three full blades and two shaped wall blades. The 2D blade shape profile of the cascade is a high-lift, low-pressure turbine L1A profile provided by the US Air Force Research Laboratories (AFRL), with a 152-mm axial chord. The Reynolds number based on the axial chord length at the nominal freestream velocity of 50 ms−1 is 500,000. A conveyor-based system was designed and fabricated to simulate the passing wakes of the upstream vanes (or blades) on the test blades (or vanes) depending on which airfoil types are put on the stationary frame and the moving frame of the conveyor. The original implementation uses blade profiles on the stationary frame and thick plate wake generators on the translating frame. Results are presented from hot-wire surveys conducted to characterize and qualify the velocity and turbulence intensity distributions and associated spectral characteristics at the cascade test section inlet, in the wake of the vanes and in the wake of the test blade. A blade instrumented with 123 pressure taps was used to acquire static pressure profiles of the cascade central blade, which were compared to the ones from the nominal airfoil design as well as to those obtained from a CFD simulation of the cascade flow. Incoming velocity and temperature profiles were found to be uniform to within a few percentage points, and the pressure coefficient distribution was found to be in good agreement with design values. The passage periodicity of the conveyor-belt-driven, flat-plates was verified and their wake was characterized. These results verified that the cascade wind tunnel operates according to design, thus proving to be a reliable test-bed for film cooling studies with and without unsteady wake effects. The design also incorporates an in-house-designed, miniature periscopic and adjustable laser sheet generating system integrated within the “dummy” blades to enable Particle Image Velocimetry measurements in the intra-blade domain.

Multirate infinitesimal step methods for atmospheric flow simulation

2009 ◽  
Vol 49 (2) ◽  
pp. 449-473 ◽  
Author(s):  
Jörg Wensch ◽  
Oswald Knoth ◽  
Alexander Galant
Keyword(s):  
Flow Simulation ◽  
Atmospheric Flow
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