Turbulent Flow in a Rotating Two Pass Smooth Channel

1999 ◽  
Vol 121 (4) ◽  
pp. 725-734 ◽  
Author(s):  
Shou-Shing Hsieh ◽  
Ping-Ju Chen ◽  
Hsiang-Jung Chin
Keyword(s):  
Flow Field ◽  
Cross Section ◽  
Flow Separation ◽  
Laser Doppler Anemometry ◽  
Centrifugal Forces ◽  
Mean Velocity ◽  
Axis Of Rotation ◽  
Smooth Channel ◽  
Measured Flow ◽  
Turbulent Air Flow

Laser-Doppler anemometry has been applied to approximately 2-D turbulent air flow in a rotating 2 pass channel of square cross section. The axis of rotation is normal to the axis of the duct, and the flow is radially outward/inward. The duct is of finite length and the walls are isothermal. Smooth channels are experimentally conducted with rotational speeds of 100, 200, and 300 rpm with ReH = 5000 and 10,000. The main features of the flow, flow separation and mean velocity as well as turbulent intensity at particular location along the downstream are presented. The measured flow field is found to be quite complex, consisting of secondary cross-stream and radially outward flows due to the Coriolis effects and centrifugal forces.

Turbulent Flow in a Rotating Two Pass Ribbed Rectangular Channel

2003 ◽  
Vol 125 (4) ◽  
pp. 609-622 ◽  
Author(s):  
Shou-Shing Hsieh ◽  
Hsiang-Jung Chin
Keyword(s):  
Laser Doppler Anemometry ◽  
Rectangular Cross Section ◽  
Rectangular Channel ◽  
Stress Distributions ◽  
Centrifugal Forces ◽  
Reattachment Length ◽  
Mean Velocity ◽  
Stream Flows ◽  
Measured Flow ◽  
Turbulent Air Flow

Laser-Doppler anemometry has been applied to approximately two-dimensional turbulent air flow in rotating two pass channel with turbulator of rectangular cross section (AR=3:1). The axis of rotation is normal to the axis of the duct, and the flow is radially outward/inward. The duct is of finite length and the walls are isothermal. Two sided oppositely ribbed channel including one sided ribbed U bend of p/e=8 at e/DH=0.27 are experimentally conducted with ReD=5000 and 10,000. The main features of the flow, reattachment length, recirculation zone, and mean velocity as well as turbulent intensity and shear stress distributions are presented in ribbed ducts. The measured flow field is found to be quite complex, consisting of secondary cross-stream flows due to the Coriolis effects and centrifugal forces with rib-roughened surfaces.

Experimental and Numerical Investigation of a Cold Turbulent Jet Impinging on a Hot Plate

2012 ◽  
Author(s):  
D. I. Maldonado ◽  
J. K. Abrantes ◽  
L. F. A. Azevedo ◽  
A. O. Nieckele
Keyword(s):  
Flow Field ◽  
Laser Doppler Anemometry ◽  
Turbulence Models ◽  
Impinging Jets ◽  
Reynolds Stresses ◽  
Hot Plate ◽  
Mean Velocity ◽  
Velocity Statistics ◽  
Reliable Assessment ◽  
Anisotropic Structures

Impinging jets are an efficient mechanism to enhance wall heat transfer, and are widely used in engineering applications. The flow field of an impinging jet is quite complex and it is a challenging case for turbulence models validation as well as measurements techniques. In the present work, a detailed investigation of a cold jet impinging on a hot plate operating in the turbulent flow regime was conducted. The flow field was characterized by both Laser Doppler Anemometry and Particle Image Velocimetry (PIV) techniques in order to collect 1st and 2nd order velocity statistics to allow a reliable assessment of the numerical simulations. Comparison was performed with two turbulence methodologies: RANS (κ–ω SST model) and LES (Dynamic Smagorinsky model). The comparison was performed to assess LES feasibility and accuracy in capturing the anisotropic structures that several tested RANS models missed. The mean velocity, instantaneous velocity, Reynolds stresses and Nusselt profiles obtained numerically are compared with experimental data. A physical insight about the general flow dynamics was obtained with the extensive amount of information available from the LES.

Effects of Density Ratio on the Hydrodynamics of Film Cooling

1990 ◽  
Vol 112 (3) ◽  
pp. 437-443 ◽  
Author(s):  
J. R. Pietrzyk ◽  
D. G. Bogard ◽  
M. E. Crawford
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Free Stream ◽  
Laser Doppler Anemometry ◽  
Density Ratio ◽  
Vertical Plane ◽  
Flux Ratio ◽  
Mean Velocity ◽  
Entire Flow ◽  
Hydrodynamic Study

This paper presents the results of a detailed hydrodynamic study of a row of inclined jets issuing into a crossflow with a density ratio of injectant to free stream of 2. Laser-Doppler anemometry was used to measure the vertical and streamwise components of velocity for a jet-to-free stream mass flux ratio of 0.5. Mean velocity components and turbulent Reynolds normal and shear stress components were measured at locations in a vertical plane along the centerline of the jet from 1 diameter upstream to 30 diameters downstream of the jet. The results, which have application to film cooling, give a quantitative picture of the entire flow field, from the approaching flow upstream of the jet, through the interaction region of the jet and free stream, to the relaxation region downstream where the flow field approaches that of a standard turbulent boundary layer.

Coriolis Effects on the Flow Field Inside a Rotating Triangular Channel for Leading Edge Cooling

2013 ◽  
Vol 136 (3) ◽  
Author(s):  
Matteo Pascotto ◽  
Alessandro Armellini ◽  
Claudio Mucignat ◽  
Luca Casarsa
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Flow Structure ◽  
Cross Section ◽  
Working Conditions ◽  
Rotation Axis ◽  
Leading Edge ◽  
Channel Cross Section ◽  
Smooth Channel ◽  
Static Conditions

The flow field inside a rotating smooth radial channel with a triangular shaped cross section is investigated. Test conditions resemble those pertaining to the passages used for the internal cooling of the gas turbine blade's leading edge. Heat transfer data are also available from the literature on the same geometry and at comparable working conditions and have been profitably used for a combined aerothermal analysis. The model consists of a straight smooth channel with an equilateral triangle cross section. The rotation axis is aligned with one of the triangle bisectors. Two dimensional particle image velocimetry (PIV) and stereo-PIV were used in order to characterize the inlet flow (in static conditions) and the rotation-induced secondary flow in the channel cross section at Re = 20,000, Ro = 0.2 and Re = 10,000, Ro = 0.4. A wider range of working conditions (Re = 10,000–40,000, Ro = 0.2–0.6) was explored by means of Reynolds averaged Navier–Stokes (RANS) simulations carefully validated by the available PIV data. The turbulence was modeled by means of the shear stress transport (SST) model with a hybrid near-wall treatment. The results show that the rotation-induced flow structure is rather complicated and show relevant differences compared to the flow models that have been considered thus far. Indeed, the secondary flow turned out to be characterized by the presence of two or more vortex cells, depending on channel location and Ro number. No separation or reattachment of these structures is found on the channel walls but they have been observed at the channel apexes. The stream-wise velocity distribution shows a velocity peak close to the lower apex and the overall flow structure does not reach a steady configuration along the channel length. This evolution is fastened (in space) if the rotation number is increased while changes of the Re number have no effect. Finally, due to the understanding of the flow mechanisms associated with rotation, it was possible to provide a precise justification of the channel thermal behavior.

Numerical Simulation on the Flow Field inside an Ultrasonic Water Meter

2013 ◽  
Vol 712-715 ◽  
pp. 1126-1130
Author(s):  
Hong Chen ◽  
Zhang Kai ◽  
Yao Ling ◽  
Hong Jun Zhang
Keyword(s):  
Flow Field ◽  
Cross Section ◽  
Pipe Flow ◽  
Field Data ◽  
Correction Coefficient ◽  
Mean Velocity ◽  
Flow Rates ◽  
Type Flow ◽  
Difference Type ◽  
Water Meter

Flow field inside an ultrasonic water meter of time-difference-type are numerically simulated at several flow rates. Linear mean velocity (LMV) averaged along the line between the transmitting transducer and the receiving one, and the surface mean velocity (SMV) averaged in the cross section of the reducing-type flow passage, and the flow correction coefficient are calculated with the flow field data obtained by the simulation. Its found that the values of flow correction coefficient for the reducing-type meter channel flow are quite different from that for a fully developed pipe flow, and are related to the flow rate or Reynolds number.

Spatiotemporal Characterization of a Conical Swirler Flow Field Under Strong Forcing

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
A. Lacarelle ◽  
T. Faustmann ◽  
D. Greenblatt ◽  
C. O. Paschereit ◽  
O. Lehmann ◽  
...  
Keyword(s):  
Flow Field ◽  
Swirling Flow ◽  
Flow Instability ◽  
Laser Doppler Anemometry ◽  
Helical Structure ◽  
Mean Velocity ◽  
Flow Measurements ◽  
Natural Flow ◽  
Flow Frequency

In this study, a spatiotemporal characterization of forced and unforced flows of a conical swirler is performed based on particle image velocimetry (PIV) and laser Doppler anemometry (LDA). The measurements are performed at a Reynolds number of 33,000 and a swirl number of 0.71. Axisymmetric forcing is applied to approximate the effects of thermoacoustic instabilities on the flow field at the burner inlet and outlet. The actuation frequencies are set at the natural flow frequency (Strouhal number Stf≈0.92) and two higher frequencies (Stf≈1.3 and 1.55) that are not harmonically related to the natural frequency. Phase-averaged measurement are used as a first step to visualize the coherent flow structures. Second, proper orthogonal decomposition (POD) is applied to the PIV data to characterize the effect of the actuation on the fluctuating flow. Measurements indicate a typical natural flow instability of helical nature in the unforced case. The associated induced pressure and flow oscillations travel upstream to the swirler inlet where generally fuel is injected. This observation is of critical importance with respect to the stability of the combustion. Harmonic actuation at different frequencies and amplitudes does not affect the mean velocity profile at the outlet, while the coherent velocity fluctuations are strongly influenced at both the inlet and outlet. On one hand, the dominant helical mode is replaced by an axisymmetric vortex ring if the flow is forced at the natural flow frequency. On the other hand, the natural flow frequency prevails at the outlet under forcing at higher frequencies and POD analysis indicates that the helical structure is still present. The presented results give new insight into the flow dynamics of a swirling flow burner under strong forcing.

Exploring and Improving the Flow Characteristics of an Empty Water Channel Test Section: The Application of TomoPIV and Flowrate Sensors for Whole-Flow-Field Visualization

2019 ◽  
Author(s):  
Seyedmohammad Mousavi sani ◽  
Navid Goudarzi ◽  
Mohammadamin Sheikhshahrokhdehkordi ◽  
Tucker Bisel ◽  
Jerry Dahlberg ◽  
...  
Keyword(s):  
Flow Field ◽  
Flow Velocity ◽  
Test Section ◽  
Water Channel ◽  
Flow Characteristics ◽  
Flow Speed ◽  
Mean Velocity ◽  
Measurement Volume ◽  
Measured Flow ◽  
Field Velocity

Abstract This paper presents the quantitative results of improving the uniformity of the flow field within the test section of a constant cross section, closed-loop water channel. Tomographic Particle Image Velocimetry (TomoPIV) and four flowrate sensors are used to determine the mean velocity and velocity fluctuations at two motor frequencies: 7.5 Hz and 10 Hz (an approximate free stream flow velocity of 0.11 m/s and 0.18 m/s, respectively). The flow field velocity determined by the flowrate sensors showed great agreements with the TomoPIV results. For instance, at the 10 Hz water channel motor frequency, the flowrate sensors and TomoPIV obtained velocity ranges of 0.191–0.202 m/s and 0.185–0.21 m/s, respectively. In order to reduce the flow speed variations within the studied TomoPIV measurement volume, improvements were implemented on the water channel to include an adjustable screen and deflector to the first set of turning vanes downstream from the water channel motor. The modification improved the 7.5 Hz motor frequency measured flow velocity from 0.16–0.172 m/s to 0.106–0.108 m/s resulting in a final variation of flow speed within the measurement volume reduced to 1%.

Hydrodynamic Measurements of Jets in Crossflow for Gas Turbine Film Cooling Applications

1989 ◽  
Vol 111 (2) ◽  
pp. 139-145 ◽  
Author(s):  
J. R. Pietrzyk ◽  
D. G. Bogard ◽  
M. E. Crawford
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Laser Doppler Anemometry ◽  
Vertical Plane ◽  
Separation Region ◽  
Mean Velocity ◽  
Stress Components ◽  
Entire Flow ◽  
Hydrodynamic Study ◽  
Field Approaches

This paper presents the results of a detailed hydrodynamic study of a row of inclined jets issuing into a crossflow. Laser-Doppler anemometry was used to measure the vertical and streamwise components of velocity for three jet-to-mainstream velocity ratios: 0.25, 0.5, and 1.0. Mean velocity components and turbulent Reynolds normal and shear stress components were measured at locations in a vertical plane along the centerline of the jet from 1 diameter upstream to 30 diameters downstream of the jet. The results, which have application to film cooling, give a quantitative picture of the entire flow field, from the approaching flow upstream of the jet, through the interaction region of the jet and mainstream, to the relaxation region downstream where the flow field approaches that of a standard turbulent boundary layer. The data indicate the existence of a separation region in the hole from which the jet issues, causing high levels of turbulence and a relatively uniform mean velocity profile at the jet exit.

Effects of Density Ratio on the Hydrodynamics of Film Cooling

1989 ◽  
Author(s):  
J. R. Pietrzyk ◽  
D. G. Bogard ◽  
M. E. Crawford
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Laser Doppler Anemometry ◽  
Density Ratio ◽  
Vertical Plane ◽  
Flux Ratio ◽  
Mean Velocity ◽  
Entire Flow ◽  
Hydrodynamic Study ◽  
Field Approaches

This paper presents the results of a detailed hydrodynamic study of a row of inclined jets issuing into a crossflow with a density ratio of injectant to freestream of two. Laser Doppler anemometry was used to measure the vertical and streamwise components of velocity for a jet-to-freestream mass flux ratio of 0.5. Mean velocity components and turbulent Reynolds normal and shear stress components were measured at locations in a vertical plane along the centerline of the jet from 1 diameter upstream to 30 diameters downstream of the jet. The results, which have application to film cooling, give a quantitative picture of the entire flow field, from the approaching flow upstream of the jet, through the interaction region of the jet and freestream, to the relaxation region downstream where the flow field approaches that of a standard turbulent boundary layer.

scholarly journals Urban Boundary Layers Over Dense and Tall Canopies

2021 ◽  
Author(s):  
Alexandros Makedonas ◽  
Matteo Carpentieri ◽  
Marco Placidi
Keyword(s):  
Packing Density ◽  
Laser Doppler Anemometry ◽  
Canopy Height ◽  
Roughness Sublayer ◽  
Average Height ◽  
Wind Tunnel Experiments ◽  
Mean Velocity ◽  
Flow Features ◽  
Stress Layer ◽  
Density Results

AbstractWind-tunnel experiments were carried out on four urban morphologies: two tall canopies with uniform height and two super-tall canopies with a large variation in element heights (where the maximum element height is more than double the average canopy height, $$h_{max}=2.5h_{avg}$$ h max = 2.5 h avg ). The average canopy height and packing density are fixed across the surfaces to $$h_{avg} = 80~\hbox {mm}$$ h avg = 80 mm , and $$\lambda _{p} = 0.44$$ λ p = 0.44 , respectively. A combination of laser Doppler anemometry and direct-drag measurements are used to calculate and scale the mean velocity profiles with the boundary-layer depth $$\delta $$ δ . In the uniform-height experiment, the high packing density results in a ‘skimming flow’ regime with very little flow penetration into the canopy. This leads to a surprisingly shallow roughness sublayer (depth $$\approx 1.15h_{avg}$$ ≈ 1.15 h avg ), and a well-defined inertial sublayer above it. In the heterogeneous-height canopies, despite the same packing density and average height, the flow features are significantly different. The height heterogeneity enhances mixing, thus encouraging deep flow penetration into the canopy. A deeper roughness sublayer is found to exist extending up to just above the tallest element height (corresponding to $$z/h_{avg} = 2.85$$ z / h avg = 2.85 ), which is found to be the dominant length scale controlling the flow behaviour. Results point toward the existence of a constant-stress layer for all surfaces considered herein despite the severity of the surface roughness ($$\delta /h_{avg} = 3 - 6.25$$ δ / h avg = 3 - 6.25 ). This contrasts with the previous literature.

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