Visualization of turbulent flow around a sphere at subcritical reynolds numbers

Jang, Young Il; Lee, S. J.

doi:10.1007/bf03181894

Cited by 14 publications

(4 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The large-scale motions are associated (among other phenomena) to wake meandering [17,26], while the development of small-scale structures (e.g., sub-rotor, f d/U ≥ 5) is due to the production of the turbulence kinetic energy induced in the shear layer of the wake. Similar phenomena have been reported for other setups, including flow passing circular and rectangular cylinders, spheres, among others [27][28][29]. The differences between the cases across scales are highlighted with the corresponding pre-multiplied spectra f Φ in Figure 3(a2-c2).…”

Section: Background Turbulence Modulation On the Wake Velocity Spectrasupporting

confidence: 81%

Effects of Freestream Turbulence in a Model Wind Turbine Wake

et al. 2016

View full text Add to dashboard Cite

Abstract:The flow structure in the wake of a model wind turbine is explored under negligible and high turbulence in the freestream region of a wind tunnel at Re ∼ 7 × 10 4 . Attention is placed on the evolution of the integral scale and the contribution of the large-scale motions from the background flow. Hotwire anemometry was used to obtain the streamwise velocity at various streamwise and spanwise locations. The pre-multiplied spectral difference of the velocity fluctuations between the two cases shows a significant energy contribution from the background turbulence on scales larger than the rotor diameter. The integral scale along the rotor axis is found to grow linearly with distance, independent of the incoming turbulence levels. This scale appears to reach that of the incoming flow in the high turbulence case at x/d ∼ 35-40. The energy contribution from the turbine to the large-scale flow structures in the low turbulence case increases monotonically with distance. Its growth rate is reduced past x/d ∼ 6-7. There, motions larger than the rotor contribute ∼50% of the total energy, suggesting that the population of large-scale motions is more intense in the intermediate field. In contrast, the wake in the high incoming turbulence is quickly populated with large-scale motions and plateau at x/d ∼ 3.

show abstract

Section: Background Turbulence Modulation On the Wake Velocity Spectrasupporting

confidence: 81%

Effects of Freestream Turbulence in a Model Wind Turbine Wake

et al. 2016

View full text Add to dashboard Cite

show abstract

“…The time interval between two pulses, t, was controlled by adjusting the delay generator. The FFT-based cross-correlation PIV technique was employed to calculate the velocity from the consecutive particle images (Jang and Lee, 2007). The size of the interrogation window was 32 32 pixels 2 , and each interrogation window was overlapped 50%.…”

Section: Experimental Methodsmentioning

confidence: 99%

Investigation on the flow characteristics inside an automotive HVAC system with varying ventilation mode

Kang

Lee

2009

J Vis

Self Cite

View full text Add to dashboard Cite

The ventilation flow in a heating, ventilation and air conditioning (HVAC) module of a passenger car was investigated experimentally. Three different ventilation modes with varying temperature mode were tested to study the effect of ventilation mode on the velocity field inside the HVAC module. For each mode, more than 450 instantaneous velocity fields were measured using a particle image velocimetry (PIV) velocity field measurement technique. The instantaneous velocity fields were ensemble averaged to obtain the spatial distribution of mean velocity and spanwise vorticity. The present work highlights the usefulness of the PIV technique for the analysis of the flow inside an HVAC module. The experimental results can be used not only to understand and improve the ventilation flow of an HVAC module but also to validate numerical predictions.

show abstract

“…Most have focused on the vortex shedding phenomena, using hot-wire anemometry to measure the dominant shedding frequencies. They have also studied wake structures, using qualitative flow visualization methods [1][2][3][4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Vibrational characteristics of sphere model installed in wind tunnel test section

Jang

Lee

2010

J Mech Sci Technol

View full text Add to dashboard Cite

The vibrational characteristics of a sphere model installed in a wind tunnel test section were quantitatively investigated using a noncontact laser vibrometer. The sphere was supported by two fine wires passing perpendicularly through the center of the model in an Xshape. Each end of the wire was fastened firmly to the frame of the test section with a secure turnbuckle. This fixation method was evaluated by laser vibrometry measurement of the vibration of the sphere and by spectral analysis. The maximum displacement of the sphere was found to be less than 30 nm with the characteristic frequency on the order of hundreds of kilohertz. The effects of the vibrational displacement and frequency of the model were negligible considering the model dimensions and the shedding frequency of the sphere wake.

show abstract

Visualization of turbulent flow around a sphere at subcritical reynolds numbers

Cited by 14 publications

References 18 publications

Effects of Freestream Turbulence in a Model Wind Turbine Wake

Effects of Freestream Turbulence in a Model Wind Turbine Wake

Investigation on the flow characteristics inside an automotive HVAC system with varying ventilation mode

Vibrational characteristics of sphere model installed in wind tunnel test section

Contact Info

Product

Resources

About