Technology and Operations
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Re: How does a submarine bank when turning to port or starboard?
Posted by:
Don Prince
()
Date: July 03, 2008 01:14AM
Hi Robert,
The book "Cambridge Ocean Technology Series 2 Concepts in Submarine Desigs" covers the Snap Roll....
Page 157
Roll Aspects
"It is not unusual to specify any requirements for control of the roll motion, though the designer needs to know the caused of the phenomenon termed 'snap roll', which we describe later, and what steps can be taken to minimize it. It is the practice to lay down a limit on maximum roll angle - 50 degrees is not untypical - to which equipment and machinery on board the submarine have to be designed. Whilst this is set as a design limit it is not acceptible for normal operation."
Page 176
"When the submerged submarine turns in a horizontal plane, the action of the bridge fin is more complex. Efforts to reduce its drag results in a streamline shape, rather like the airfoil section of a wing of low aspect ratio, which will generate lift when at an angle of attack to the flow. Those circumstances arise in a turn when the hull is in general drift motion and because the sideways lift force on the bridge fin acts well above the axis of the submarine a heeling moment results. The drift angle on a submarine in a tight turn can build up quite quickly and the dynamics of the corresponding heeling moment from the bridge fin can cause a 'snap roll' which although it is inward on the turn can be far larger than is appropriate for a banked turn effect."
The book covers the design varibles that will help eliminate the snap roll phenomenon.
Regards,
Don_
"A man's got to know his limitations..."
Harry Callahan, SFPD
The book "Cambridge Ocean Technology Series 2 Concepts in Submarine Desigs" covers the Snap Roll....
Page 157
Roll Aspects
"It is not unusual to specify any requirements for control of the roll motion, though the designer needs to know the caused of the phenomenon termed 'snap roll', which we describe later, and what steps can be taken to minimize it. It is the practice to lay down a limit on maximum roll angle - 50 degrees is not untypical - to which equipment and machinery on board the submarine have to be designed. Whilst this is set as a design limit it is not acceptible for normal operation."
Page 176
"When the submerged submarine turns in a horizontal plane, the action of the bridge fin is more complex. Efforts to reduce its drag results in a streamline shape, rather like the airfoil section of a wing of low aspect ratio, which will generate lift when at an angle of attack to the flow. Those circumstances arise in a turn when the hull is in general drift motion and because the sideways lift force on the bridge fin acts well above the axis of the submarine a heeling moment results. The drift angle on a submarine in a tight turn can build up quite quickly and the dynamics of the corresponding heeling moment from the bridge fin can cause a 'snap roll' which although it is inward on the turn can be far larger than is appropriate for a banked turn effect."
The book covers the design varibles that will help eliminate the snap roll phenomenon.
Regards,
Don_
"A man's got to know his limitations..."
Harry Callahan, SFPD
