“…The stream-wise velocity magnitudes enhance close to the bottom rigid boundary for larger mesh size ( G 1 ). This signifies that the velocities overshoot here and is the result of the alternate wake and the formation of jet pattern that gets advected from the grid wires 44,45 for the current flow case. As the distances increases along the downstream of the grid, the overshooting nature of the flow decreases and the data almost merges with without grid flow cases.…”
The investigation presents the estimate of the degree of deviation from the isotropic turbulence in terms of Reynolds stress tensor for grid generated turbulence under the influence of bottom boundary. The turbulence triangle, Eigen values, and the invariant functions are presented at near and far field regions of the grids with different solidity ratio. In addition, the work also deals with the analysis based on third-order moments of the velocity fluctuations and the ratio of momentum flux to the turbulent kinetic energy in the frequency domain. The Reynolds stress anisotropy exposes that the anisotropic invariant maps possess a closed looping trend in the near field region and an open looping trend in the far-field region of the grid. Further, to describe the physical behaviour of the velocity time-series of random fluctuating components in the stream-wise directions, the probability distribution function are estimated and interpreted.
“…The stream-wise velocity magnitudes enhance close to the bottom rigid boundary for larger mesh size ( G 1 ). This signifies that the velocities overshoot here and is the result of the alternate wake and the formation of jet pattern that gets advected from the grid wires 44,45 for the current flow case. As the distances increases along the downstream of the grid, the overshooting nature of the flow decreases and the data almost merges with without grid flow cases.…”
The investigation presents the estimate of the degree of deviation from the isotropic turbulence in terms of Reynolds stress tensor for grid generated turbulence under the influence of bottom boundary. The turbulence triangle, Eigen values, and the invariant functions are presented at near and far field regions of the grids with different solidity ratio. In addition, the work also deals with the analysis based on third-order moments of the velocity fluctuations and the ratio of momentum flux to the turbulent kinetic energy in the frequency domain. The Reynolds stress anisotropy exposes that the anisotropic invariant maps possess a closed looping trend in the near field region and an open looping trend in the far-field region of the grid. Further, to describe the physical behaviour of the velocity time-series of random fluctuating components in the stream-wise directions, the probability distribution function are estimated and interpreted.
“…Here, M 1, M 2 and M 3 correspond to smaller, medium and the largest mesh sizes, respectively. The detailed information of the grid materials, solidity ratio ðÞ of the grids and the mounting arrangement of instruments used for the present investigation is provided in the Raushan et al 13,15 The measurement locations were constant at different downstream distance from the grids (Figure 1). The turbulence generated by different mesh size at the downstream of the grids changed from non-homogeneous velocity field close to the grid to homogeneous and isotropic (within a close approximation) turbulence in the FF region.…”
Section: Experimentation and Measurement Descriptionmentioning
confidence: 99%
“…The detailed information of the grid materials, solidity ratio (σ) of the grids and the mounting arrangement of instruments used for the present investigation is provided in the Raushan et al. 13,15 Figure 1.Experimental facility of water channel facility for study the grid-generated turbulence under bottom boundary flow.…”
Section: Experimentation and Measurement Descriptionmentioning
confidence: 99%
“…Thereafter, Panda 12 developed a complete model for the pressure strain correlation for inhomogeneous turbulent flows where the effects of boundaries and walls are important. Recently, Raushan et al 13 investigated experimentally the behaviour of turbulence generated by grid in oscillatory flow. The experimental result suggested that the turbulence energy produced in the decay region is efficiently transported to the outward direction.…”
Section: Introductionmentioning
confidence: 99%
“…Recently, Raushan et al. 13 investigated experimentally the behaviour of turbulence generated by grid in oscillatory flow. The experimental result suggested that the turbulence energy produced in the decay region is efficiently transported to the outward direction.…”
The present study aims to investigate the flow characteristics of grid-generated turbulence under the consideration of solid boundary in free surface flow. To understand the nature of isotropy and anisotropy in the flow, the turbulent intensity is evaluated at the downstream of the grid for different mesh sizes. The energy spectrums based on the Fast Fourier and marginal Hilbert–Huang transform are presented to understand the decay of energy in the associated spectral frequency domain. It is observed that the peak of energy associated with the Fourier spectrum decreases in the near-field region of the grid with the increase in mesh size of the grid. Further, to characterise the concentrated velocity fluctuations, the paper strives to analyse the joint probability distribution function and the local intermittency measure in the close and far stream of the grid. The autocorrelation functions and the magnitude of integral length scale of the stream-wise fluctuating velocity components are also presented at two different vertical levels from the solid boundary. The normalised Shannon entropy is also evaluated to characterise the degree of the orderness or disorderness in the flow due to the interaction of grid and rigid boundary.
An experimental approach was performed to examine the interaction between the rigid boundary and grid turbulence of different mesh sizes. Three unlike mesh sizes (M 1 , M 2 and M 3 ) were used having a constant diameter (d) and crosssection. Variation of mean velocities in stream-wise and vertical direction, turbulent intensities, Reynolds shear stresses and turbulence kinetic energy at the different locations of the grid M 1 , M 2 and M 3 are discussed. The time series of velocity was measured by an acoustic Doppler velocimetry (ADV). The measured data of velocity fluctuations were used to understand the variations of turbulent characteristics behind the grids with rigid boundary interaction.
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