ORCID Profile
0000-0001-8724-6684
Current Organisation
The University of Auckland
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Publisher: IOP Publishing
Date: 09-2020
DOI: 10.1088/1742-6596/1618/6/062004
Abstract: A transient simulation of a two inline wind turbines during the evening transition period is modelled using Large Eddy Simulation with an actuator disc method. Two inline turbines are placed parallel to the stream-wise direction and the distance between the turbines is seven rotor diameters. The wind profiles and turbulence data are produced by a precursor simulation. The simulation was carried out for four physical hours and the surface heat flux varies with time according to the evening period. The wind profile evolves over the transition period and the atmospheric stability gradually changes from unstable in the late afternoon to a stable condition in the evening. The wake recovers more quickly in the afternoon and it recovers more slowly corresponding to the changes in atmospheric stability. This causes a reduction in the power output and the mean thrust load of the downstream turbine over the period. Additionally, the velocity spectrum displays higher fluctuations at the downstream turbine.
Publisher: IOP Publishing
Date: 09-2020
DOI: 10.1088/1742-6596/1618/6/062025
Abstract: Evaluation of the performance of the WRF model is carried out for simulating the surface winds and the diurnal cycle of wind speed for the small island developing state of Fiji at a 1.33 km by 1.33 km grid resolution using 1deg gridded data from NCEP-FNL. Simulations are performed for an austral summer (January 2017) and an austral winter (July 2017) month using the dynamical downscaling and the two-way nested approach. A set of physics parameterization schemes together with topo_wind = 1, 2 and ysu_topdown_pblmix = 1 physics settings associated with YSU PBL scheme are used to correct the surface winds and the diurnal cycle of wind speed. The results reveal that the WRF model is able to capture the surface winds and the diurnal cycle of wind speed on the windward side. Surface winds on the leeward side and the outer islands, show positive bias especially at nighttime for January and at both the day and night time for July. The statistical evaluation of all stations for January (July) showed a bias of 1.16 m/s (1.89 m/s), RMSE of 2.40 m/s (3.14 m/s), STDE of 1.88 m/s (2.08 m/s) and diurnal cycle correlation of 0.74 (0.68) using topo_wind = 2 and ysu_topdown_pblmix = 1.
Publisher: Elsevier BV
Date: 03-2013
Publisher: The Royal Society
Date: 08-2017
Abstract: The structure of turbulence in a rapid tidal flow is characterized through new observations of fundamental statistical properties at a site in the UK which has a simple geometry and sedate surface wave action. The mean flow at the Sound of Islay exceeded 2.5 m s −1 and the turbulent boundary layer occupied the majority of the water column, with an approximately logarithmic mean velocity profile identifiable close to the seabed. The anisotropic ratios, spectral scales and higher-order statistics of the turbulence generally agree well with values reported for two-dimensional open channels in the laboratory and other tidal channels, therefore providing further support for the application of universal models. The results of the study can assist in developing numerical models of turbulence in rapid tidal flows such as those proposed for tidal energy generation.
Publisher: The Royal Society
Date: 28-02-2013
Abstract: This paper analyses a set of velocity time histories which were obtained at a fixed point in the bottom boundary layer of a tidal stream, 5 m from the seabed, and where the mean flow reached 2.5 m s −1 . Considering two complete tidal cycles near spring tide, the streamwise turbulence intensity during non-slack flow was found to be approximately 12–13%, varying slightly between flood and ebb tides. The ratio of the streamwise turbulence intensity to that of the transverse and vertical intensities is typically 1 : 0.75 : 0.56, respectively. Velocity autospectra computed near maximum flood tidal flow conditions exhibit an f −2/3 inertial subrange and conform reasonably well to atmospheric turbulence spectral models. Local isotropy is observed between the streamwise and transverse spectra at reduced frequencies of f .5. The streamwise integral time scales and length scales of turbulence at maximum flow are approximately 6 s and 11–14 m, respectively, and exhibit a relatively large degree of scatter. They are also typically much greater in magnitude than the transverse and vertical components. The findings are intended to increase the levels of confidence within the tidal energy industry of the characteristics of the higher frequency components of the onset flow, and subsequently lead to more realistic performance and loading predictions.
Publisher: Elsevier BV
Date: 12-2018
Publisher: Informa UK Limited
Date: 24-10-2017
Publisher: Elsevier BV
Date: 05-2015
Publisher: Elsevier BV
Date: 10-2021
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 2019
DOI: 10.2514/1.C034813
Publisher: IEEE
Date: 05-2010
Publisher: IEEE
Date: 12-2010
Publisher: Elsevier BV
Date: 04-2016
Publisher: Elsevier BV
Date: 11-2018
Publisher: Elsevier BV
Date: 07-2021
No related grants have been discovered for Rajnish Sharma.