scholarly journals Wind Tunnel Measurement of Turbulent and Advective Scalar Fluxes: A Case Study on Intersection Ventilation

2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
Libor Kukačka ◽  
Štĕpán Nosek ◽  
Radka Kellnerová ◽  
Klára Jurčáková ◽  
Zbyněk Jaňour
Keyword(s):  
Wind Tunnel ◽  
Flow Direction ◽  
Quadrant Analysis ◽  
High Temporal Resolution ◽  
Scalar Flux ◽  
Concentration Data ◽  
Measured Velocity ◽  
Scalar Fluxes ◽  
Wind Tunnel Measurement ◽  
Street Intersection

The objective of this study is to determine processes of pollution ventilation in the X-shaped street intersection in an idealized symmetric urban area for the changing approach flow direction. A unique experimental setup for simultaneous wind tunnel measurement of the flow velocity and the tracer gas concentration in a high temporal resolution is assembled. Advective horizontal and vertical scalar fluxes are computed from averaged measured velocity and concentration data within the street intersection. Vertical advective and turbulent scalar fluxes are computed from synchronized velocity and concentration signals measured in the plane above the intersection. All the results are obtained for five approach flow directions. The influence of the approach flow on the advective and turbulent fluxes is determined. The contribution of the advective and turbulent flux to the ventilation is discussed. Wind direction with the best dispersive conditions in the area is found. The quadrant analysis is applied to the synchronized signals of velocity and concentration fluctuation to determine events with the dominant contribution to the momentum flux and turbulent scalar flux.

Effect of Blade Tip Geometry on Tip Flow and Heat Transfer for a Blade in a Low Speed Cascade

2003 ◽  
Author(s):  
Vikrant Saxena ◽  
Hasan Nasir ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Wind Tunnel ◽  
Flow Direction ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Transfer Coefficients ◽  
Wake Effect ◽  
Low Speed ◽  
Heat Transfer Coefficients ◽  
Blade Tip

A comprehensive investigation of the effect of various tip sealing geometries is presented on the blade tip leakage flow and associated heat transfer of a scaled up HPT turbine blade in a low-speed wind tunnel facility. The linear cascade is made of four blades with the two corner blades acting as guides. The tip section of a HPT first stage rotor blade is used to fabricate the 2-D blade. The wind tunnel accommodates an 116° turn for the blade cascade. The mainstream Reynolds number based on the axial chord length at cascade exit is 4.83 × 105. The upstream wake effect is simulated with a spoked wheel wake generator placed upstream of the cascade. A turbulence grid placed even farther upstream generates the required free-stream turbulence of 4.8%. The center blade has a tip clearance gap of 1.5625% with respect to the blade span. Static pressure measurements are obtained on the blade surface and the shroud. The effect of crosswise trip strips to reduce leakage flow and associated heat transfer is investigated with strips placed along the leakage flow direction, against the leakage flow and along the chord. Cylindrical pin fins and pitch variation of strips over the tip surface are also investigated. Detailed heat transfer measurements are obtained using a steady state HSI-based liquid crystal technique. The effect of periodic unsteady wake effect is also investigated by varying the wake Strouhal number from 0. to 0.2, and to 0.4. Results show that the trip strips placed against the leakage flow produce the lowest heat transfer on the tips compared to all the other cases with a reduction between 10–15% compared to the plain tip. Results also show that the pitch of the strips has a small effect on the overall reduction. Cylindrical pins fins and strips along the leakage flow direction do not decrease the heat transfer coefficients and in some cases enhance the heat transfer coefficients by as much as 20%.

scholarly journals NUMERICAL AND EXPERIMENTAL ANALYSIS OF THE FLOW OVER A COMMERCIAL VEHICLE - PICKUP

2018 ◽  
Vol 17 (2) ◽  
pp. 92
Author(s):  
W. J. G. S. Pinto ◽  
O. Almeida
Keyword(s):  
Wind Tunnel ◽  
Flow Pattern ◽  
Reverse Flow ◽  
Flow Direction ◽  
Original Data ◽  
Cfd Simulations ◽  
Flat Surfaces ◽  
Sharp Edges ◽  
Recirculation Zones ◽  
Low Speed Wind Tunnel

This work presents an ongoing numerical and experimental study of the flow around a pickup vehicle by means of CFD simulations and wind tunnel experiments. The model was based on the light-pickup market in Brazil and it was designed with flat surfaces and sharp edges. One of the objectives of this research was the understanding about the flow pattern around the vehicle, especially in the region behind the cabin and the wake. Another goal was to obtain original data from experimental measurements which could be used on further computational investigations. The experiments were carried out in a low-speed wind tunnel at Reynolds number of 5 x 105. Hot-wire anemometry was used to obtain the velocity profiles. Wall tufts were applied to describe the flow direction and regions of attached/detached and recirculation zones. Acceleration due to the underbody and the shear layer formed on the cabin were well defined, also indicating a region of reverse flow behind the tailgate. The flow visualization allowed the identification of recirculation regions inside the trunk and regions of detached flow. These flow patterns were also reproduced in the CFD simulations resulting satisfactory information to describe the main flow pattern over the pickup vehicle.

An Improved Correction Method for Sound Source Drift in A Jet Flow and Its Application to A Wind Tunnel Measurement

2015 ◽  
Vol 101 (3) ◽  
pp. 642-649 ◽  
Author(s):  
Yigang Wang ◽  
Jiashun Yang ◽  
Qing Jia ◽  
Zhigang Yang ◽  
Zhe Shen
Keyword(s):  
Wind Tunnel ◽  
Sound Source ◽  
Jet Flow ◽  
Correction Method ◽  
Wind Tunnel Measurement

scholarly journals A force-balance study of ice flow and basal conditions of Jutulstraumen, Antarctica

1996 ◽  
Vol 42 (142) ◽  
pp. 413-425 ◽  
Author(s):  
Øyvind Armand Høydal
Keyword(s):  
Flow Direction ◽  
Bottom Topography ◽  
Effective Strain ◽  
Great Influence ◽  
Force Balance ◽  
Effect Of Temperature ◽  
Velocity Variation ◽  
Shear Stresses ◽  
Balance Study ◽  
Measured Velocity

Abstract Stresses and velocities at depth are calculated across Jutulstraumen, an ice stream in Dronning Maud Land, draining about 1% of the Antarctic ice sheet. The force-balance study is based on data from kinematic GPS measurements on three strain nets, each consisting of 3 × 3 stakes. The maximum measured velocity is 443 m a−1 and the velocity variation over short distances is large compared with studied ice streams in West Antarctica. The surface topography together with the measured velocities across the profile indicate that the bottom topography has a great influence on the flow direction, even where the ice thickness is more than 2000 m. The basal shear stresses are calculated as 180, 227 and 146 kPa in the three Strain nets, while the corresponding driving stresses are 180, 122 and 111 kPa (±5%). The heat produced by sliding and internal deformation is sufficient to keep the base at the pressure-melting point. The annual basal melting is estimated to be about 60 mm. Investigations on the effect of temperature softening show that the flow parameter’s influence on the effective strain rate is more important than the flow parameter’s direct softening in the flow low alone. The mass flow calculated by the force-balance method is between 87 and 96% of pure plug flow and total discharge is calculated to be 13.3 ± 10 km3a-1.

On the Response of Horizontal and Vertical Axis Wind Turbines to Turbulence: A Wind Tunnel Experiment

2014 ◽  
Author(s):  
Nicolas A. Tobin ◽  
Rishabh Narang ◽  
Leonardo P. Chamorro
Keyword(s):  
Wind Tunnel ◽  
Turbulent Flow ◽  
Vertical Axis ◽  
High Temporal Resolution ◽  
Flow Conditions ◽  
Physical Processes ◽  
University Of Illinois ◽  
Flow Modulation ◽  
Vertical Axis Wind Turbines ◽  
The University

The turbulent flow modulation on the unsteady behavior of a model VAWT is investigated and compared with a model HAWT of similar size in a laboratory experiment. The turbines operated in low and high freestream turbulence. The research was performed at the Talbot Laboratory wind tunnel at the University of Illinois at Urbana-Champaign (UIUC). High-resolution measurements of the turbine voltage for a small, 12 cm HAWT and a 16 cm VAWT are acquired at high temporal resolution, sufficient to capture the turbulent scales of flow relevant to the problem. Both turbines were built at the UIUC rapid prototyping lab and have realistic airfoil shapes. An understanding of the distinctive physical processes modulating the scale-to-scale fluctuating behavior in a VAWT and a HAWT exposed to the same turbulent flow conditions is discussed. A relation between turbulent motions and fluctuating behavior is extended from the knowledge of HAWTs to VAWTs.

Effect of Blade Tip Geometry on Tip Flow and Heat Transfer for a Blade in a Low-Speed Cascade

2004 ◽  
Vol 126 (1) ◽  
pp. 130-138 ◽  
Author(s):  
Vikrant Saxena ◽  
Hasan Nasir ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Wind Tunnel ◽  
Flow Direction ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Transfer Coefficients ◽  
Wake Effect ◽  
Low Speed ◽  
Heat Transfer Coefficients ◽  
Blade Tip

A comprehensive investigation of the effect of various tip sealing geometries is presented on the blade tip leakage flow and associated heat transfer of a scaled up HPT turbine blade in a low-speed wind tunnel facility. The linear cascade is made of four blades with the two corner blades acting as guides. The tip section of a HPT first stage rotor blade is used to fabricate the two-dimensional blade. The wind tunnel accommodates an 116 deg turn for the blade cascade. The mainstream Reynolds number based on the axial chord length at cascade exit is 4.83×105. The upstream wake effect is simulated with a spoked wheel wake generator placed upstream of the cascade. A turbulence grid placed even farther upstream generates the required freestream turbulence of 4.8%. The center blade has a tip clearance gap of 1.5625% with respect to the blade span. Static pressure measurements are obtained on the blade surface and the shroud. The effect of crosswise trip strips to reduce leakage flow and associated heat transfer is investigated with strips placed along the leakage flow direction, against the leakage flow and along the chord. Cylindrical pin fins and pitch variation of strips over the tip surface are also investigated. Detailed heat transfer measurements are obtained using a steady-state HSI-based liquid crystal technique. The effect of periodic unsteady wake effect is also investigated by varying the wake Strouhal number from 0. to 0.2, and to 0.4. Results show that the trip strips placed against the leakage flow produce the lowest heat transfer on the tips compared to all the other cases with a reduction between 10–15% compared to the plain tip. Results also show that the pitch of the strips has a small effect on the overall reduction. Cylindrical pins fins and strips along the leakage flow direction do not decrease the heat transfer coefficients and in some cases enhance the heat transfer coefficients by as much as 20%.

Heat Transfer Effects During Cold Dense Gas Dispersion: Wind-Tunnel Simulation of Cold Gas Spills

1986 ◽  
Vol 108 (1) ◽  
pp. 9-15 ◽  
Author(s):  
R. N. Meroney ◽  
D. E. Neff
Keyword(s):  
Heat Transfer ◽  
Wind Speed ◽  
Wind Tunnel ◽  
Transfer Effects ◽  
Concentration Data ◽  
Gas Dispersion ◽  
Humidity Effects ◽  
Low Wind Speed ◽  
Wind Tunnel Simulation ◽  
Heat Transfer Effects

Wind-tunnel concentration data were obtained for continuous area releases of ambient temperature Freon–air mixtures, cold N2, cold CO2, and cold CH4 clouds. Heat transfer and humidity effects on model concentration distributions were significant for methane plumes when surface Richardson numbers Ri* were large (i.e., low wind speed and high boiloff rate conditions). At field scales heat transfer and humidity will still play a role in the dispersion of methane spill cases, but plume dilution and liftoff are not expected to be as exaggerated as for the model cases.

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