Physical modeling of complex airflows developing above rural terrains

Kozmar, Hrvoje

doi:10.1007/s10652-011-9224-1

Cited by 23 publications

(8 citation statements)

References 34 publications

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“…There are nevertheless cases in which the phenomena under study are too complicated to rely exclusively on computational simulations. Physical models are still being built to study environmental phenomena such as soil erosion [6][7] , atmospheric flows over rural terrains, 8 physiological systems and processes, [9][10] and technological procedures in metallurgy [11][12] and drilling. 13 We are interested in physical-model simulations for a different reason: we want to build models that can be perceived with our senses (sight, primarily) of phenomena that can only be observed with the aid of special tools, or for which direct component-level observations are not possible.…”

Section: Physical-model Simulationsmentioning

confidence: 99%

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A macroscopic device described by a Boltzmann-like distribution

et al. 2013

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Equilibrium thermodynamic phenomena such as the Maxwell-Boltzmann distribution of molecular velocities are rare in systems of macroscopic particles interacting by mechanical collisions. This paper reports a system composed of millimeter-sized polymer objects that under mechanical agitation exhibits a "discretization" of the configurations of the system, and has a distribution of the probabilities of these configurations that is analogous to a Boltzmann distribution. The system is composed of spheres and a three-link chain on a bounded horizontal surface, shaken with an aperiodic but not completely random horizontal motion. Experiments were performed at different strengths of agitation (quantified by the frequency of agitation, f, at constant amplitude) and densities of spheres (quantified by the filling ratio, FR). The chain was typically found in one of three conformationsextended, single folded, and double foldedbecause, under collisions with the spheres, adjacent links were stable mechanically only when fully extended or fully folded. The probabilities of the different conformations of the chain could be described by a Boltzmann distribution in which the "temperature" depended on f and the "energies" of conformations on FR. The predictions of the Boltzmann formula using empirically determined "temperatures" and "energies" agreed with measurements within two experimental standard deviations in 47 out of 48 experiments.

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Section: Physical-model Simulationsmentioning

confidence: 99%

“…We calculated the energies E 2,MA and E 3,MA of the C2 and C3 conformations according to eqn (8), where n f is the number of non-zero probability measurements carried at a given frequency f (n f = 3 or 4). The dependence of the energy levels on FR, shown in Fig.…”

Section: Modeling the Statistics Of Chain Conformations With A Boltzmmentioning

confidence: 99%

A macroscopic device described by a Boltzmann-like distribution

et al. 2013

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“…The flow and the turbulence were analyzed with respect to the mean velocity, turbulence intensity, Reynolds stress, integral length scales of turbulence, and power spectral density of velocity fluctuations, as this set of ABL parameters allows for a comprehensive analysis of ABL characteristics, e.g. [36], [37], [38], [39], [40]. The ABL velocity profiles without the hill model were normalized using the reference velocity u in the lower ABL (above the displacement height), as this way of normalization is common when studying ABL wind tunnel simulations.…”

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confidence: 99%

Wind Characteristics in the Wake of a Non-Rotating Wind Turbine close to a Hill

Kozmar

Allori

Bartoli

et al. 2019

TFAMENA

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Hilly terrain may considerably influence energy yield and structural loading of wind turbines. Wind energy developers are therefore required to accurately predict wind characteristics at the wind farm site already in the designing phase. It is necessary to determine how particular hill shape and size affect wind characteristics at the location of wind turbines operating in the wake of a hill. In order to address this complex issue, small-scale laboratory experiments were carried out in a boundary layer wind tunnel (BLWT). The focus was on characteristics of the flow at the same position downstream of the hill and the wind turbine models studied on various sizes and shapes of the hill model. Three hill models (a small and a large hill with laterally uniform heights and a hill with a bay) were exposed to the thermally neutrally stratified atmospheric boundary layer (ABL) simulation. In each experiment, there was only one hill model in the BLWT test section. The configuration without the hill, i.e. the flat terrain model, was tested as a reference case. Downstream of the hill model, there was a single (alone-standing) wind turbine model. Flow characteristics were studied downstream (behind) the wind turbine model. The wind turbine model was in the parking position in order to study wind characteristics in the situation with a strong wind when there is no rotation of rotor blades. The experimental results indicate a velocity decrease and stronger turbulence in the wind turbine wake in the presence of a hill, which trend is more pronounced in the case of larger hills. Strong velocity gradients are observed around the hub height in the large hill configuration, while this velocity deficit is the smallest in the hill with a bay configuration due to flow channeling. The velocity power spectra reveal the characteristic peak due to the vortex shedding from the hill ridge. The obtained results provide a new insight into the turbulent wake characteristics of a single wind turbine placed downstream of a hill with a potential to serve as a validation tool for computational studies.

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“…The ABL simulation length scale factor calculated as suggested by Cook 17 is 300. The ABL parameters reported at the model scale are z 0 = 6 mm, d = 50 mm, and α = 0.26, whose values were calculated using the procedure outlined in Kozmar 18 …”

Section: Methodsmentioning

confidence: 99%

The effect of parked wind turbines on wind flow and turbulence over a complex terrain

2021

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Wind‐tunnel experiments were performed to study the wind characteristics on a parked wind turbine downwind of three types of hill and over a flat terrain. The focus of the study is on comparing wind characteristics on (a) a wind turbine standing alone and (b) this same type of wind turbine embedded in a wind farm. Particular emphasis is placed on the hill size and shape and the distance between the hill and the wind farm. The hill and wind‐farm models were subjected to an atmospheric boundary layer simulation to create realistic atmospheric conditions. Flow and turbulence were analyzed based on the measured mean flow velocity, Reynolds shear stress, turbulence intensity, and the power spectral density of velocity fluctuations. The experimental results reveal similar trends concerning (a) the wind characteristics obtained on a parked wind turbine embedded in a wind farm downwind of hills of various sizes and shapes and (b) the wind characteristics on this same type of parked wind turbine standing alone in the same position downwind of the same hills. In particular, the discrepancies in the mean flow velocity and turbulence intensity between these test cases are mostly below 5%, thus indicating that a complex terrain clearly has a dominant effect on the wind characteristics, while the effects of parked wind turbines on the wind characteristics are negligible. This important finding indicates that the structural loading of parked wind turbines situated on a complex terrain may be well calculated using the same procedures both for wind turbines standing alone and wind turbines embedded in wind farms if they are both placed at the same distance downwind of the same hills.

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Physical modeling of complex airflows developing above rural terrains

Cited by 23 publications

References 34 publications

A macroscopic device described by a Boltzmann-like distribution

A macroscopic device described by a Boltzmann-like distribution

Wind Characteristics in the Wake of a Non-Rotating Wind Turbine close to a Hill

The effect of parked wind turbines on wind flow and turbulence over a complex terrain

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