What is wake fraction?
marine. The speed of advance of the propeller “VA” relative to the water in which it is working is lower than the observed speed of the vessel “V”. This difference in speed, expressed as a percentage of the ship speed, is known as the wake fraction coefficient “w”.
What is KT and KQ?
Dependent variables that should be modeled simultaneously are thrust coefficient (KT) and torque coefficient (KQ). By definition, these coefficients are interrelated (linked) through the expression for the open water efficiency—ηO = (KT/KQ) · (J/2π).
What is wake in ship?
What is a ship wake? A moving ship (or any other object moving at or near the water surface) generates a kind of trace on the water surface which is called a wake. Around and directly behind the ship, the wake is rather complex, with so-called bow and stern waves, eddies and currents, and foam.
What is wake distribution?
The wake distribution is measured behind the ship model using pitot tubes or laser-Doppler velocimetry. The results are usually displayed as contour lines of the longitudinal component of the velocity. These data plays an important role in the propeller design.
What is speed of advance ship?
Speed of advance is the speed a ship would travel through the water at any given shaft rotation, not taking into account any external forces such as set and drift.
What is skew of propeller?
Skew angle of a propeller is the angle measured from ray “A” passing through the tip of the blade at mid-chord line to ray “B” tangent to the mid-chord line on the projected blade outline. See also Propeller.
What is propeller torque?
Propeller torque can be one of the most prominent left turning tendencies. Because of Newton’s Third Law of motion, the force that the engine exerts to rotate the propeller (the torque) is met with a reactive force that is exerted back on the engine, and therefore the entire airplane.
What is a wake in aerodynamics?
The wake is the region of disturbed flow (often turbulent) downstream of a solid body moving through a fluid, caused by the flow of the fluid around the body. Parachutes deployed into wakes suffer dynamic pressure deficits which reduce their expected drag forces.
What is wake width?
verb wakes, waking, woke or woken. (often foll by up) to rouse or become roused from sleep. (often foll by up) to rouse or become roused from inactivity. (intr; often foll by to or up to) to become conscious or awareat last he woke to the situation. (intr) to be or remain awake.
What is nominal wake?
Nominal wake refers to the flow field in the propeller plane at ship stern, when the ship is towed in the absence of propeller. The computations can be performed at model scale, full scale, or at model scale with extrapolation to full scale wake by means of semi-empirical wake scaling methods.
What is SOA in navigation?
Speed of advance (SOA) is used to indicate the speed to be made along the intended track. SOA is also used to designate the average speed that must be made good to arrive at a destination at a specified time.