T.M. No. 125 - January 1961 



Transient Wind Tides in Shallow Water by E. G. Tickner 



Transient wind tides were studied in a laboratory channel with 

 various water depths and wind velocities. The studies were divided 

 into two parts, the first being concerned with the surface time 

 history and the second the transient water motion. Results of the 

 first part indicate water surface "setup" will overshoot its steady 

 state value by a factor of 2, being slightly higher for deeper water 

 depths and lower for shallower water depths. Harder's theory is 

 adequate for predicting shallower water setup history, but not for 

 deeper depths. Results of the second part of the study indicate 

 the surface current reaches steady state very quickly and has a 

 value of 1/30 of the average wind velocity passing over the surface 

 for Reynold's number 2 x I 0^ or greater. The water also oscillates 

 and its oscillatory magnitude can be predicted by using standard 

 wave equations with the. wave height as the maximum setup. A return 

 flow in the lower layers overcomes the slowly damped oscillatory 

 motion and a steady state flow is established. 



T.M. No. 124 - March 1961 



Experimental Study on the Solitary Wave Reflection Along a Straight 

 Sloped Wall at Oblique Angle of Incidence by T. C. Chen 



The reflection pattern of a solitary wave impinging on a sloping 

 wall and some accompanying phenomena were studied in a laboratory 

 ripple tank. The angle of incidence of the wave was varied between 

 zero and 90° and the slope angle of the wall with the horizontal, 

 between 20° and 150°. It was found that curved ripples developed 

 when Incident waves hit a wall of slope less than 65° approximately. 

 As the angle of incidence increased, an envelope of these ripples 

 formed and became large enough beyond a certain angle of incidence, 

 depending on slope, to look li ke a reflected wave but remained 

 curved as were the ripples. For a relatively steep wall slope, 

 larger than 65°, reflection was regular, but the angle of incidence 

 at which a straight, reflected wave occurred depended on the slope 

 of the wall. For a wall with negative slope Mach reflection took 

 place for wave incident angles between 30° and 35°. Mach reflection 

 ceased and regular reflection occurred when the angle of incidence 

 was 45°. Three types of wave behavior relative to breaking were 

 observed and found to be related to the angle of incidence. 



T.M. No. 125 - March 1961 



On the Description of Short-Crested Waves by J . E. Chappelear 



A mathematical description of short-crested waves is presented, 

 based on the procedure of Fuchs which has been systematized using 

 the procedure of Stokes (a formal power-series expansion about the 

 case of zero height). The solution presented has a limitation to 



37 



