A large tank of water containing 800 ppm salt is connected to a tank distilled water through a narrow tube about 6 cm long. The pressure of the system is adjusted so that there is no mass movement of the fluid. Which is the approximate flux density [mg/(cm2 s)] of this salt due to molecular diffusion once the salt gradient in the tube stabilizes? Assume that D = 10-5 cm2/s

feed back to aid with ques-  (a) In this question a suspension is settling over time. As time progresses the volume of the clear layer at the top of the cylinder will increase. You know that the clear layer has a cylindrical shape. Therefore, you can calculate the height of the clear layer at each volume given using the equation for the volume of a cylinder. You are told that you can calculate the single particle velocity at time point 1 which corresponds to the point where the volume of the clear layer is 29 mL.     answers  Time (s)  0,1.6,5.3, 26.4

14. A bubbly mixture of gas and liquid flows up a vertical glass tube with an internal diameter of 25 mm. The liquid flow is controlled to be 0.02 litres per second, and the gas flow is 10 litres per second. The bubble velocity is determined photographically to have a velocity of 30 ms-¹. Determine the gas void fraction for the two-phase mixture and the liquid velocity. Answer: 0.68, 0.13 ms-¹

3 A constant-density Newtonian fluid is flowing as a thin film down a vertical wall in laminar flow; see Fig. 15.9. a. Find the velocity distribution and the volumetric flow rate per unit width of wall by using the Navier-Stokes equations (z component) on the assumptions that there is no flow in the x or y direction, that the z component of the velocity is zero at the solid wall, and that there is no shear stress at the liquid-air surface, and the flow is steady-state. (Waves may appear on the fluid surface in this situation; ignore that possibility for this problem). Solid wall * Air Thin liquid film Thickness Ax FIGURE 15.9 A thin liquid film flowing down a wall. b. Repeat the solution to Prob. 3a, showing both the velocity distribution and the volumetric flow rate, for the case in which the flow under the influence of gravity is between two parallel vertical plates, separated by the distance Ax. In Prob. 15.9 the pressure gradient in the flow direction was zero, because the film was…