On the use of Irwin and Preston wall shear stress probes in turbulent incompressible flows with pressure gradients

Monteiro, Joaquim; Viegas, Domingos X.

doi:10.1016/s0167-6105(96)00091-8

Cited by 17 publications

(7 citation statements)

References 9 publications

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“…These sensors measure the skin friction imposed by the wind close to the surface by measuring a near‐surface pressure differential, which enables estimation of surface shear stress in complex, nonuniform airflows [ Walker and Nickling , 2003]. Irwin sensors have been used successfully to estimate near surface shear stress in several laboratory wind tunnel and field studies [ Monteiro and Viegas , 1996; Wyatt and Nickling , 1997; Crawley and Nickling , 2003; McKenna Neuman , 2003; Gillies et al , 2006, 2007]. The instrument consists of a 12.5 mm diameter brass cylinder with a 2.57 mm center tap operating as a surface pressure port.…”

Section: Methodsmentioning

confidence: 99%

A wind tunnel examination of shear stress partitioning for an assortment of surface roughness distributions

2008

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[1] Surface roughness aids to ameliorate wind erosion by extracting a portion of the wind's momentum thereby reducing the quantity of stress on the surface. This paper evaluates the effect of different spatial arrangements of surface roughness on the partition of average drag forces and distribution of stress at the surface. A new tiered force balance was used in a wind tunnel to independently and simultaneously measure the drag on arrays of roughness elements and the drag on the intervening surface. In addition, Irwin sensors recorded point measurements of surface shear stress within the arrays. Roughness arrays consisted of small cylinders in four different spatial arrangements, one being staggered and three being simplifications of natural roughness configurations, at four roughness densities. Results from the tiered force balance and Irwin sensors indicate that the roughness configuration has a small impact on the average (R) and maximum (R 00 ) drag partition. The protection of the surface increased with roughness density regardless of the roughness arrangement. Point measurements of shear stress revealed that the roughness configuration had a small impact on the distribution of shear stress at the surface, and that the maximum shear stress scaled to the average shear stress. Drag partition measurements were compared to the ratios predicted by the Raupach et al. (1993) model and a good degree of agreement was found for all configurations when using measured values of the b and m parameter.

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Section: Methodsmentioning

confidence: 99%

A wind tunnel examination of shear stress partitioning for an assortment of surface roughness distributions

2008

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“…The Irwin sensor is a simple, omni‐directional skin friction meter that measures the near surface vertical pressure gradient [ Irwin , 1980]. Once calibrated, the Irwin sensor can be used to measure surface shear stress at frequencies greater than 10 Hz [ Irwin , 1980; Wu and Stathopoulos , 1994] and has been used successfully in a variety field and wind tunnel studies with varying flow conditions and surface roughness configurations [ Irwin , 1980; Wu and Stathopoulos , 1994; Monteiro and Viegas , 1996; Wyatt and Nickling , 1997; Crawley and Nickling , 2003]. The dynamic pressure differential is measured between two ports, one at the surface and the other at a height of 0.00175 m above the surface.…”

Section: Methodsmentioning

confidence: 99%

Aeolian sediment transport through large patches of roughness in the atmospheric inertial sublayer

Gillies¹,

Nickling²,

King³

2006

J. Geophys. Res.

107

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[1] Roughness influences the flux of wind-driven sand transport. In this paper, we report on sediment transport measurements for four different surface roughness configurations composed of the same size (solid) roughness elements in the atmospheric inertial sublayer. Results of these tests indicate that sediment transport rates through patches of roughness in the atmospheric inertial sublayer are to a large extent controlled and scale proportionally with the roughness density (l = n b h/S, where n is number of elements of breadth b and height h in area S) of the surface. However, element size apparently increases the magnitude of the reduction beyond that attributable to l. A sediment transport model that incorporates the effect of shear stress partitioning appears to predict reasonably well the effect of roughness on sand transport in the cases where the roughness elements are 0.10 m in height. However, when the dimensions of the roughness itself are equivalent to or are greater than the range of saltation lengths (vertical and horizontal), additional interactions of the elements with the saltation cloud appear to reduce the transport efficiency.

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“…Surface shear stress was measured using surface-mounted, Irwin-type differential pressure (dP) sensors (Irwin, 1981) (Figures 2a, 3c). These sensors are used typically in wind tunnel simulations to estimate surface pressure and speed of pedestrian-level winds around buildings (Monteiro and Viegas, 1996). The sensor body consists of a 19 mm diameter brass cylinder with a 2·57 mm centre tap acting as an inset surface pressure port.…”

Section: Methodsmentioning

confidence: 99%

Simulation and measurement of surface shear stress over isolated and closely spaced transverse dunes in a wind tunnel

Walker

Nickling

2003

Earth Surf Processes Landf

134

117

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Topographic interactions generate multidirectional and unsteady airflow that limits the application of velocity profile approaches for estimating sediment transport over dunes. Results are presented from a series of wind tunnel simulations using Irwin-type surface-mounted pressure sensors to measure shear stress variability directly at the surface over both isolated and closely spaced sharp-crested model dunes. Findings complement existing theories on secondary airflow effects on stoss transport dynamics and provide new information on the influence of lee-side airflow patterns on dune morphodynamics.For all speeds investigated, turbulent unsteadiness at the dune toe indicates a greater, more variable surface shear, despite a significant drop in time-averaged measurements of streamwise shear stress at this location. This effect is believed sufficient to inhibit sediment deposition at the toe and may be responsible for documented intermittency in sand transport in the toe region. On the stoss slope, streamline compression and flow acceleration cause an increase in flow steadiness and shear stress to a maximum at the crest that is double that at the toe of the isolated dune and 60-70 per cent greater than at flow reattachment on the lower stoss of closely spaced dunes. Streamwise flow accelerations, rather than turbulence, have greater influence on stress generation on the stoss and this effect increases with stoss slope distance and with incident wind speed. Reversed flow within the separation cell generates significant surface shear (30-40 per cent of maximum values) for both spacings. This supports field studies that suggest reversed flow is competent enough to return sediment to the dune directly or in a deflected direction. High variability in shear at reattachment indicates impact of a turbulent shear layer that, despite low values of time-averaged streamwise stress in this region, would inhibit sediment accumulation. Downwind of reattachment, shear stress and flow steadiness increase within 6 h (h = dune height) of reattachment and approach upwind values by 25 h. A distance of at least 30 h is suggested for full boundary layer recovery, which is comparable to fluvial estimates.The Irwin sensor used in this study provides a reliable means to measure skin friction force responsible for sand transport and its robust, simple, and cost-effective design shows promise for validating these findings in natural dune settings.

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On the use of Irwin and Preston wall shear stress probes in turbulent incompressible flows with pressure gradients

Cited by 17 publications

References 9 publications

A wind tunnel examination of shear stress partitioning for an assortment of surface roughness distributions

A wind tunnel examination of shear stress partitioning for an assortment of surface roughness distributions

Aeolian sediment transport through large patches of roughness in the atmospheric inertial sublayer

Simulation and measurement of surface shear stress over isolated and closely spaced transverse dunes in a wind tunnel

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