Effect of turbulence characteristics in the atmospheric surface layer on the peak wind loads on heliostats in stow position

Emes, Matthew; Ghanadi, Farzin; Kelso, Richard

doi:10.1016/j.solener.2017.08.031

Cited by 42 publications

(27 citation statements)

References 20 publications

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“…The boundary layers were generated using two different sets of truncated spires and a staggered arrangement of roughness elements within a test section of 3 m × 3 m cross-section and 17 m development length at the University of Adelaide wind tunnel. Mean velocity and turbulence intensity profiles closely represent ESDU 85020 [8] profiles at the position of the instrumented heliostat model in Figure 1a with constant elevation axis height = 0.5 m and chord length = 0.8 m [9]. The mean velocity profiles of the two simulated ABLs are shown by Jafari et al [2] to approximate a logarithmic profile corresponding to a flat "open country" terrain ( 0 = 0.018 m) and a suburban terrain ( 0 = 0.35 m in Figure 1a) at measurement heights 0.15 m ≤ ≤ 0.65 m. Jafari et al [2] showed that the turbulence intensities in the longitudinal direction = / (13% and 26%) and vertical direction = / (9% and 11%) in the two simulated ABLs are within the allowable bandwidth of ±20% from the predicted values in ESDU 85020 [8].…”

Section: Methodsmentioning

confidence: 67%

Wind load design considerations for the elevation and azimuth drives of a heliostat

Emes

Jafari

Arjomandi

2020

AIP Conference Proceedings

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This paper investigated the dynamic fluctuations of the high-frequency surface pressure and force measurements on an instrumented scale-model heliostat within a turbulent ABL generated in a wind tunnel. Peak aerodynamic load coefficients on the model heliostat calculated following the equivalent static wind load method were consistent with previous wind tunnel studies in the literature. The dynamic analysis of the hinge, azimuth and overturning moments in the current study showed that there are a range of critical load cases and heliostat configurations that need to be considered to investigate the dynamic loading on the elevation and azimuth drives of a heliostat. Quasi-steady variation of the fluctuating peak loads following a Gaussian distribution was found to under-predict the maximum hinge and overturning moments in operating and stow configurations. It is therefore recommended that the analysis of instantaneous loads on the elevation drive and pedestal foundation is carried out for an improved estimation of the heliostat design wind loads.

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Section: Methodsmentioning

confidence: 67%

Wind load design considerations for the elevation and azimuth drives of a heliostat

Emes

Jafari

Arjomandi

2020

AIP Conference Proceedings

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“…Large variation in tests has been attributed to difference in Reynolds number, turbulence spectrum, geometric scaling ratio, etc. While studying the influence of turbulence characteristics on peak wind loads on heliostats, wind tunnel tests were performed, the turbulence intensity and size of the largest vortices had a noticeable effect on peak pressures, compared to other parameters Reynolds number [61]. For solar panels, peak pressures in the wind tunnel were underestimated compared to full-scale data [62].…”

Section: Wind Tunnel Testingmentioning

confidence: 99%

Aerodynamics of Low-Rise Buildings: Challenges and Recent Advances in Experimental and Computational Methods

Aly¹,

Khaled²,

Gol-Zaroudi³

2021

Aerodynamics

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Buildings are bluff bodies, compared to streamline objects, such as airfoil. Wind flow over buildings leads to separation and hence a complex spatial and temporal mechanism that governs the nature and intensity of aerodynamic forces. This complexity mainly comes from the transient nature of incident turbulent winds and the fluctuating flow pattern in the separation bubble. The study of building aerodynamics is vital for the evaluation of cladding pressures, drag, shear, and uplift forces that are essential for safe and economic design. Flow separation makes it challenging to estimate loads without referring to direct physical and/or computational simulation. For several decades, aerodynamic testing has been employed for the estimation of wind pressures and forces on buildings. However, for residential homes and low-rise buildings, it has been always a challenge to predict full-scale pressures by traditional wind tunnel testing, as per the lack of large turbulence and Reynolds number effects, among other factors. The mismatch in flow physics makes it difficult to scale up wind-induced loads as the process can be highly nonlinear, which is the case when full-scale pressure coefficients do not meet those from small-scale aerodynamic testing. This chapter presents the challenges in the modeling and evaluation of aerodynamic forces on low-rise buildings, along with recent advances in both experimental and computational methods.

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“…As shown in Figure 1(b), for instance the measured peak drag coefficient from the two studies differ by 30%. Furthermore, Emes et al (2017) found that the peak lift coefficient on a heliostat at zero elevation angle increased from 0.3 to 0.83 as the model characteristic length decreased from 0.8 m to 0.3 m at a constant turbulence intensity (𝐼 𝑢 =12.5%). The increase in the peak lift coefficient was attributed to the increase of the ratio of turbulent integral length scale to the model dimension (Emes et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Measurement of unsteady wind loads in a wind tunnel: Scaling of turbulence spectra

Jafari

Ghanadi

Emes

et al. 2019

Journal of Wind Engineering and Industrial Aerodynamics

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Effect of turbulence characteristics in the atmospheric surface layer on the peak wind loads on heliostats in stow position

Cited by 42 publications

References 20 publications

Wind load design considerations for the elevation and azimuth drives of a heliostat

Wind load design considerations for the elevation and azimuth drives of a heliostat

Aerodynamics of Low-Rise Buildings: Challenges and Recent Advances in Experimental and Computational Methods

Measurement of unsteady wind loads in a wind tunnel: Scaling of turbulence spectra

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