At some corner compartments, Re~1000Re~1000
for the square tank, Re~600Re~600 for the ‘J’-type tank. At the start of each experiment, the tank was filled with clear water, and then a dilute methylene blue dye solution (concentration of 0.1 mg/l) was pumped into the tank via the inlet. Images were taken at a rate of 7.5 frames per second by selleck an Allied Vision Dolphin machine vision and saved as a BMP file every 100 frames. Matlab Image Processing Toolbox was employed to analyse these images. The experiments involved measuring the fraction of initial water in each compartment that is flushed out when water is injected into the tank. With the help of the inclined mirror, the camera captured a plan view of the tank. Dye water was injected into the tank (see Kamada et al., 2004). An optical method was used to assess
the mass of dye within buy NVP-BEZ235 each compartment based on the classical absorption theory of Lambert–Beer (see Cenedese and Dalziel, 1998, Rahim et al., 2010, Zeng et al., 2010 and Suhling et al., 2001). The image processing was based on the principle that the depth integrated dye concentration in water can be related to the intensity of light passing through the water and the distance travelled by the light in the water. The dye concentration in the water at point (x ,y ) can then be related to the change in light intensity through equation(17) CI(x,y)=∫0lC(x,y,z)dz=f(logI0(x,y)I(x,y)),where l is the distance in the z -direction that the light travels in the water, I 0 is the light intensity after the light travels through clear water, and I is the light intensity after the light travels through dye water. The function f (x ) is determined by a series of calibration tests for fixed l . The volume averaged flushed fraction in compartment [i ][j ] is equation(18) C[i][j](T)=∫A[i][j]CIdA∫A[i][j]CI,ηdA,where CI,ηCI,η is the depth integrated selleck chemical dye concentration when compartment [i][j] is completely filled with dye water, calculated from (17), and A[i][j] is the base area of compartment [i][j]. The main point was to determine
the fraction of initial fluid in each compartment that is removed, as a function of time. The diagnostic tools defined in Section 2.2 to analyse the model predictions were applied to analyse the experimental data. For images captured from the experiments, each compartment from the plan view was individually masked so that its time series (18) could be evaluated. We estimated T1/2,[i][j]T1/2,[i][j] by interpolating C[i][j]C[i][j] to determine when C[i][j]=0.5C[i][j]=0.5. We estimated α1/2,[i][j]α1/2,[i][j] by linearly regressing C[i][j]C[i][j] with T over the interval |C[i][j]−0.5|≤0.1|C[i][j]−0.5|≤0.1 and identified α1/2,[i][j]α1/2,[i][j] proportional to the slope of the curve. The major experimental measurement errors are caused by masking and calibration.