Crest height

The crest height is similar to the height of water overflowing a dam. It is calculated from... 

Crest height = 0.4 (GPM/inch (outlet) weir length)067... 

The sum of the crest height plus the weir height equals the depth of liquid on the tray deck. One might now ask, Is not the liquid level on the inlet side of the tray higher than the liquid level near the outlet weir While the answer is Yes, water does flow downhill, we design the tray to make this factor small enough to neglect. 

Crest height of liquid overflowing the outlet weir. 

The weight of liquid on a tray is created by the weir height plus the crest height. We have defined the crest height (in inches of clear liquid) in Chap. 1, as... 

As illustrated, liquid accumulates on the low side of this tray. Vapor, taking the path of least resistance, preferentially bubbles up through the high side of the tray deck. To prevent liquid from leaking through the low side of the tray, the dry tray pressure drop must equal or exceed the sum of the weight of the aerated liquid retained on the tray by the weir plus the crest height of liquid over the weir plus the 2-in out-of-levelness of the tray deck. 

Each tray in a tower is inherently a vapor-liquid redistributor. The outlet weir, or more exactly the crest height of the liquid overflowing the weir forces the liquid to flow evenly across the tray. Even if the weir... 

Multichordal downcomers can increase weir length (Fig. 6). Fig. 6 shows a combined multichordal and stepped downcomer. The increased weir length decreases the liquid crest height over the weir. This decreases total tray pressure drop. The stepping is a variation of a sloped downcomer. The step increases the downcomer inlet area with a minimum decrease in tray active area. 

Capacity factor Figure 10-29 Crest height over weir Eq. M 0-261 Downcomer pressure drop Eq. (10=27)... 

Its wave crest height is larger than 65% of of its wave height. 

The seiche oscillations in Rotterdam Harbor give rise to some practical concerns. First, water levels used for the design of dikes (in particular their crest height) are required by law to contain an allowance for seiches, superposed on the astronomical high water level (spring tide) and wind setup. The appropriate measure of this allowance is not well known. 

Meteorological measurements and visual inspection of weather charts show that all seiche episodes in Rotterdam Harbor (arbitrarily defined as a seiche-event in which the crest height exceeded 0.25 m at ROZ, a criterion that was applied in several previous studies of seiches at this location) coincided with low-pressure... 

For vertical walls, transmission is primarily governed by the relative crest height with little or no effect of wave period or steepness. A simple vertical structure has been used as an example with Hm0,i = 3 m. Overtopping and wave transmission are compared in Fig. 14.12, where in the calculations the crest height has been changed to calculate wave transmission as well as wave overtopping. 

Fig. 14.26. Overtopping for wave return wall with So = 0.04, seaward angle of 45°, a width of 2 m and a crest height oi Rc = Z m. For HmO toe = 3 m, the overtopping can be estimated from...

Fig. 15.6. Percentage of overtopping waves for rubble mound breakwaters as a function of relative (armor) crest height and armor size Rc < Ac).

The equilibrium profile of shingle beaches under (temporary constant) wave conditions is described by van der Meer. The most important profile parameter for run-up and overtopping is the crest height above SWL, he- For shingle with Dnso < 0.1m, this crest height is only a function of the wave height and wave... 

Rc = crest height above still water level,... 

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