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Urban runoff (re)mobilises solids present on the street surface and transport them to urban drainage systems. The solids reduce the hydraulic capacity of the drainage system due to sedimentation and on the quality of receiving water bodies due to discharges via outfalls and combined sewer overflows (CSOs) of solids and associated pollutants. To reduce these impacts, gully pots, the entry points of the drainage system, are typically equipped with a sand trap, which acts as a small settling tank to remove suspended solids. This study presents data obtained using Particle Image Velocimetry (PIV) and Laser Doppler Anemometry (LDA) measurements in a scale 1:1 gully to quantify the relation between parameters such as the gully pot geometry, discharge, sand trap depth, and sediment bed level on the flow field and subsequently the settling and erosion processes. The results show that the dynamics of the morphology of the sediment bed influences the flow pattern and the removal efficiency in a significant manner, prohibiting the conceptualization of a gully pot as a completely mixed reactor. Resuspension is initiated by the combination of both high turbulent fluctuations and high mean flow, which is present when a substantial bed level is present. In case of low bed levels, the overlaying water protects the sediment bed from erosion., Sanitary Engineering

Urban runoff (re)mobilises solids present on the street surface and transport them to urban drainage systems. The solids reduce the hydraulic capacity of the drainage system due to sedimentation and on the quality of receiving water bodies due to discharges via outfalls and combined sewer overflows (CSOs) of solids and associated pollutants. To reduce these impacts, gully pots, the entry points of the drainage system, are typically equipped with a sand trap, which acts as a small settling tank to remove suspended solids. This study presents data obtained using Particle Image Velocimetry (PIV) and Laser Doppler Anemometry (LDA) measurements in a scale 1:1 gully to quantify the relation between parameters such as the gully pot geometry, discharge, sand trap depth, and sediment bed level on the flow field and subsequently the settling and erosion processes. The results show that the dynamics of the morphology of the sediment bed influences the flow pattern and the removal efficiency in a significant manner, prohibiting the conceptualization of a gully pot as a completely mixed reactor. Resuspension is initiated by the combination of both high turbulent fluctuations and high mean flow, which is present when a substantial bed level is present. In case of low bed levels, the overlaying water protects the sediment bed from erosion., Sanitary Engineering

In this study, the wave amplitude dependency on a ship advancing in regular head waves with different amplitudes is investigated by Experimental Fluid Dynamics (EFD) method. The thrust, towing force and 3DOF (Degree of Freedom) motions as well as the flow field around the stern of KVLCC2 (KRISO Very Large Crude-oil Carrier2) tanker model advancing at design Froude number, Fr=0.142 are measured. Three wavelengths; λ/L=1.1, 1.6 and 2 are selected and for each wavelength five different wave amplitudes; A=0.75, 1.5, 3, 4 and 4.3 are used. The motions and force measurement was done for with and without propeller conditions whereas the SPIV (Stereo-Particle Image Velocimetry) measurement was done for without propeller condition. The motions and force measurement results were analyzed by Fourier series expansion and the data was reconstructed by ignoring the higher harmonics than 7th harmonics to understand the fluctuation shape in one period. It was noted that the 1st, 2nd and 3rd harmonic components are responsible for the thrust oscillations with a quickly increasing slope and a slowly decreasing slope. For motions, the 1st harmonic components were enough to obtain the original motion trend. The 1st harmonic values for heave and pitch motions increase linearly with increase in wave amplitude. On the other hand, the thrust mean values decrease slightly with increase in wave amplitude. For the PIV results, the vertical relative motion between the propeller disk and the low velocity region, due to bilge vortices, was observed. As the wave amplitude increases this relative motion increases and high velocity flow enters the propeller plane from the bottom. In conclusion, the velocity distribution around the stern was analysed and discussed with respect to the thrust fluctuation in waves. The trend could be explained although the velocity field was measured for without propeller condition.

Average velocity distributions of the turbulent swirl flow for four Reynolds numbers, obtained with one-component laser Doppler anemometry (LDA) and stereo particle image velocimetry (SPIV) behind axial fan in the pipe, has been reported in this paper. The highest levels of turbulence are observed in the vortex core region as well the non-Gaussian values for skewness and flatness factors. Additional information on turbulent structure physics were obtained on the basis of experimentally determined autocorrelation functions and time integral scale for circumferential velocity.

Turbulent swirl flow in the field of hydraulic machines and systems occupies attention of many researchers in laboratories and industry, as it has significant influence on energy consumption and fan design. Physical understanding of this phenomenon would enlighten many unsolved problems and help developing new turbulent numerical models for CFD analysis. Distribution and mutual influences of the time averaged and fluctuation velocity fields to each other have been investigated in this paper. Test rig is consisted of circular pipe sections with total length 27.74·D, where D=0.4m is pipe inner diameter. Specially designed axial fan, which generates Rankine’s type swirl, is positioned at the test rig inlet following profiled free-bell mouth inlet. Stereo Particle image velocimetry (SPIV) and one-component Laser Doppler Anemometry (LDA) have been conducted in the measuring section x/D=3.35 from the test rig inlet. In this paper is presented vortex core dynamics for five Reynolds numbers defined with five equally distributed fan rotation numbers in the interval n=500 till 2500rpm. Criterion of minimum total velocity has been employed. Percentage of the unique points remain almost constant for all five regimes. Distribution of the statistical moments of higher order, determined on the basis of LDA measurements, gives better understanding of the turbulent swirl velocity field. Visualization with Nd:Yag laser, max 30fps camera and paraffin oil has been performed in the cross section x/D=26.31 for better understanding of the vortex core dynamics.