Consider the velocity field of Problem 2.18. Plot the streamline formed by particles that passed through the point (1, 1) during the interval from t = 0 to t = 3 s. Compare with the streamlines plotted through the same point at the instants t = 0, 1, and 2 s.

To save energy, the air supply to a 2000 ft office has been shut off overnight and the room temperature has dropped to 40°f. in the morning, the thermostat is reset to 70°f and warm air at 120 f begins to flov in at 200ft'/min. the air is well mixed within the room, and an equal mass flow of air at room temperature (changing with time) is withdrawn through a return duct. the air pressure is nearly 1 atm everywhere. ignoring heat transfer with the surroundings and kinetic and potential energy effects, estimate how long it takes for the room temperature to reach 70°f. plot the room temperature as a function of time.