Near wall characterization of the flow over a two-dimensional steep smooth hill

Loureiro, Juliana; Pinho, F.T.; Freire, Atila P. Silva

doi:10.1007/s00348-007-0252-z

Cited by 24 publications

(33 citation statements)

References 32 publications

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“…The reattachment point x R locates at about x R /H 6.0 ± 0.3. Similar wind-tunnel experiments on a two-dimensional hill model show that the reattachment points are located at 4.82 [4], 5.25 [6] and 6.67 [10]. However, it should be noted that the location strongly depends on the ratio of the inflow boundary layer thickness to the hill height δ/H, the shape of the hill (steepness of hill slope), and the surface roughness condition (smooth or k-type, d-type).…”

Section: Experimental Apparatusmentioning

confidence: 75%

“…With a view to the atmospheric boundary layer studies, the ratio would normally be set to an order of 10 [1,2,9]. On the other hand, some studies, devoted to the engineering interest in the separation bubble, set the ratio to an order of one [10]. In the present study, we focus on the turbulent heat transfer around the separation bubble, the ratio is set to δ/H = 0.5.…”

Section: Experimental Apparatusmentioning

confidence: 99%

“…Figure 14 shows the local wavelet spectrum of the temperature variance near the wall. As shown in (10), the time average of the local spectrum directly relates to the Fourier spectrum multiplied by the frequency (Fig. 13).…”

Section: Thermal Field Statisticsmentioning

confidence: 99%

“…In the channel flow, however, the inflow is strongly affected by the separation upstream of the hill; moreover, the outer-layer characteristics of the inflow generally differ from those of an external (boundary layer) flow. Regarding the experiment of an incoming turbulent boundary layer flow over a single hill model, Loureiro et al [10] recently examined the nearwall turbulent statistics, including the wall shear stress, using a one-component LDV with a forward-scatter mode in a water tunnel. The detailed near-wall data were used for assessment of various turbulence models [25].…”

Section: Introductionmentioning

confidence: 99%

“…In order to extract elementary processes hidden in complex fields, we focus on the characteristics of the turbulent flow over a simple hill model. There are many studies on the turbulent flows over both two-dimensional (2D) [1][2][3][4][5][6][7][8][9][10][11] and three-dimensional (3D) hill models [2,[12][13][14][15][16]. Informative review papers appraise the present situation on the flow field over hills [17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

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Turbulent Heat and Fluid Flow over a Two-Dimensional Hill

Houra

Nagano

2009

Flow Turbulence Combust

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Experimental investigation has been made on the flow and thermal fields over a heated two-dimensional hill with a cosine-squared shape. The detailed turbulent characteristics are measured by a backscatter-type two-component LDV, a PIV system, a fine thermocouple and a cold-wire probe. In the reverse-flow region on the leeward side of the hill, the turbulence intensities and the Reynolds shear stress show much larger values than in a canonical wall-bounded shear flow. The mean temperature maintains a relatively high value below the location where the horizontal mean velocity rapidly decreases. At the outer edge of the reverse-flow region, there exists a second maximum intensity of temperature fluctuations. The instantaneous temperature waveforms near the heated surface show very large amplitude consisting of high-frequency fluctuations superimposed on the low-frequency motions. Simultaneous measurement of velocity and temperature is also done using a combination of a two-component LDV and a fine-wire thermocouple together with digital response compensation. In the downstream region of the hill, the horizontal and vertical turbulent heat fluxes become maximum at the hill-top height, and tend to diffuse in the vertical direction. On the other hand, in the reverse-flow region formed behind the hill, both of the heat fluxes decrease remarkably. In particular, it is worth noting that the horizontal turbulent heat flux near the surface becomes opposite in sign to that in the forward flow region. This is mainly due to the reversal of the mean flow direction. Nomenclature C pwall static pressure coefficient,height of a two-dimensional hill L half width of a two-dimensional hill P probability density function P mean pressure P 0 reference inlet pressure R θ Reynolds number based on momentum thickness T, T instantaneous and mean temperatures T w , T ∞ wall and ambient temperatures t fluctuating temperature, t = T − T t fluctuating temperature normalized by rms value,t = t/t rms

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Section: Experimental Apparatusmentioning

confidence: 75%