Direct Numerical Simulation of Isothermal Wake: DNS Noise, Strong Anisotropy Turbulence, and Vortex Dislocation Generation Mechanism

Noto, Katsuhisa

doi:10.1080/10407790903116402

Cited by 5 publications

(48 citation statements)

References 18 publications

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“…Due to the above STAD, vortex spirals (SPs) and wake become 3-D, and SPs have vortex dislocations (VDs). In fact, the viewpoint of STA was employed in the isothermal wake in [3] and was successful.…”

Section: Previous Studies On Turbulence Anisotropymentioning

confidence: 97%

“…The [42] is the sequel of [43], which shows that DNSs are employed to examine GW instability dynamics at a high intrinsic frequency, wave amplitudes both above and below nominal convective instability, and Reynolds number sufficiently high to allow a fully developed turbulence spectrum. [3] on cylinder wake. Up to the present, previous studies on STA, i.e., the strong TA, in the cylinder wake are only [3] (2009), where DNS was done and the isothermal wake at Re ¼ 300 is found to have STA degree (STAD), determined by comparing TAs.…”

Section: Previous Studies On Turbulence Anisotropymentioning

confidence: 99%

“…[3] on cylinder wake. Up to the present, previous studies on STA, i.e., the strong TA, in the cylinder wake are only [3] (2009), where DNS was done and the isothermal wake at Re ¼ 300 is found to have STA degree (STAD), determined by comparing TAs. Due to the above STAD, vortex spirals (SPs) and wake become 3-D, and SPs have vortex dislocations (VDs).…”

Section: Previous Studies On Turbulence Anisotropymentioning

confidence: 99%

“…Only three studies have been reported. One is the study by Noto (2009) [3] in the isothermal wake at Re ¼ 300. The other is in the flow field with the magnetic field in [44,45], which are not on the wake.…”

Section: Studymentioning

confidence: 99%

“…(3) and (13) The isothermal time-dependent Karman vortex street in a circular cylinder wake is two-dimensional (2-D), laminar, has a continuous spanwise vortex spiral (SP) at 44 < Re < 180, becomes three-dimensional (3-D), has turbulence at 180 < Re, and has discontinuous spanwise SP [1-3] and vortex dislocations (VDs) [1][2][3][4] at Re ¼ 270 [4] or 300 [1][2][3]. VDs were first shown by experimental streaklines [4], were next shown by direct numerical simulation (DNS) computed streaklines [1][2][3], are 3-D [1 -3], are in the transitional state [3], and have strong turbulence anisotropy (STA). Here the wake is the flow arising in the downstream behind a body, SP is the circulating streaklines along the cylinder axis, and the isothermal wake has the cylinder temperature T 0 w , which is equal to the mainstream temperature T 0 1 .…”

Section: Introductionmentioning

confidence: 97%

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Direct Numerical Simulation of Air Heated Cylinder Wake in Transitional State. Part I: Cylinder Heating Effect on Strong Turbulence Anisotropy (STA), and Determination of STA Suppression

Noto

2014

Numerical Heat Transfer, Part B: Fundamentals

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A variation of strong turbulence anisotropy (STA) with cylinder heating, and, as a result, STA suppression, are here first elucidated in the air heated wake in the transitional state at Reynolds number Re ¼ 300 and Richardson number Ri ¼ 0.3. Simultaneously, new facts for variations of velocities u, v, and w, i.e., the upward, horizontal, and spanwise directions, and wake motion by cylinder heating are first elucidated. Here STA is defined such that, in velocities u, v, and w, laminar velocities arise in at least one directions but turbulence arises in the remainder of directions.1. STA is determined to arise in isothermal and heated wakes by employing the new method. With cylinder heating, STA is found to be suppressed because the turbulent region in w is decreased, the three-dimensionality is suppressed, but the twodimensionality and laminarization are enhanced in the heated wake. 2. With cylinder heating, the spanwise velocity jwj is found to be suppressed strongly in the probability density function (PDF), whose peak value is decreased strongly near w % 0, and becomes 20% of that in the isothermal wake. 3. The above decrease in jwj is found to be equivalent to the increase of laminar state in time records. With cylinder heating, the laminar region is increased, but the region with turbulence is decreased. 4. The wake stability is extremely different in thermal flows with or without turbulence in w. When w has turbulence, here u and v are laminar, STA arises, and the thermal flow field becomes the transitional state, has instability, and is destabilized. 5. When w does not have turbulence, and is laminar, velocities u, v, and w are all laminar, form only 3-D flow, and do not have turbulence anisotropy. The wake does not have instability, and is stabilized.

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Section: Previous Studies On Turbulence Anisotropymentioning

confidence: 97%