Fluid Flow

raised. The Liquid will have a meniscus, which is the curved area of the liquid in a capillary tube because of its adhesive forces and surface tension. The meniscus will be downward in mercury and upward in water. Figure 64shows the meniscus of water:

Figure 64.

The smaller the radius of the capillary tube, the greater is the height of the liquid because a smaller tube will hold less mass. In addition, the greater the fluid density, the less the liquid will rise in the capillary tube. This means that the height is inversely proportional to the density and inversely proportional to radius.

FLUID FLOW

The flow rate, as defined by the letter Q, is the volume of a fluid passing through an area divided by the time. The SI units for flow rate of a fluid is meters cubed per second. There are many other units used for flow rate used in other circumstances, such as liters per minute or liters per second. In a tube, it is the area of the tube times the average velocity of the liquid.

Flow rate is different from velocity. The greater the velocity of the water in a river, the greater the flow rate; however, the flow rate depends on the size of the river. The actual relationship between the average velocity and the flow rate is that the flow rate is the cross-sectional area times the velocity. The larger the conduit, the greater the flow rate.