Oscillating Valved Disk Propulsion. The last propulsion means that 

 was investigated for deep -ocean cable burial is an application of an 

 innovative idea called the Alveolator concept [42]. In essence, when 

 a body (such as a disk) is accelerated through a fluid, there is a mass 

 of the fluid which must also be accelerated. This is an ''added'' or 

 virtual mass. In the case of a disk accelerated through water, the added 

 mass term is given by 



M = K p ^ r^ 

 a d w 3 



where M = added mass 

 a 



Kj = added mass coefficient (1.2) 

 p = mass density of water 

 r = disk radius 



The acceleration of this significant mass produces a force that may be 

 used to drive a second body to which the disk is attached. If the disk is 

 valved such that the valves are closed when the acceleration is in a 

 direction to provide the desired force (Figure 5) , and the valves are open 

 when the disk is accelerated in the opposite direction, a net driving force 

 is produced. A mathematical model was developed for a cable-burying machine 

 (plow) propelled by an Alveolator disk. Representative values were selected 

 for machine weight, soil shearing and viscous forces, and drag forces. A 

 digital analysis performed on the computer showed that the system moved 

 along the seafloor with a net velocity of 0.25 ft /sec, but that the motion 

 was oscillatory with an amplitude of nearly 4 feet. Optimization of the 

 system parameters and the driving function may reduce or eliminate the 

 machine oscillation and increase the speed. The major drawbacks of this 

 system are the engineering difficulties involved in implementing the 

 valved disk means and that the concept is unproven except by mathematical 

 simulation. Note that if the machine is fitted with a plow, the plow 

 vibrates due to the vibration of the machine, and the force required for 

 plowing may reduce considerably due to plow vibration. The computer results 

 showed that the average power required for propulsion and excavation is 

 172 hp. Since the driving function for the disk has a large amplitude 

 (5 feet) and low frequency (1 Hertz) , a double-acting hydraulic ram can 

 be used as the prime mover. 



Running Gear Subsystems 



A major component of the resistance to forward motion for a cable 

 burial machine is the interaction between the machine's running gear 

 and the soil . 



Skids. The mechanism for predicting the resistance between a skid 

 and the seafloor is not well established, but is generally considered to 

 be dominated by friction in sandy soils and be shearing resistance in 

 clay soils; that is, 



28 



