RESISTANCE OF SHIP

-

 

          Resistance of ship is the opposing force experienced by the body while moving through liquid.

Types of Resistance:-
1. Wave making resistance
2. Frictional resistance
3. Viscous pressure drag
4. Eddy making resistance
5. Appendage resistance
6. Wind making resistance

Methods to find resistance:-
l) From model test 
    - done in towing tanks
    - models attached to the carriage
    - platform has a dynamometer from which resistance is measured
    - resistance tests are done in smooth water


2) From methodical series
       - test starts with a parent form
       - a number of significant form parameters are varied
       - results show how resistance varies with form parameters
       - useful for estimating power for new designs


Different methodical series
     - Taylor series
     - BSRA series
     - Gulhammer & Harward series
     - DTMB series


Using Gulhammer & Harward series

Step 1:-

   Residual resistance coefficient and frictional resistance coefficient are found out using series diagrams

Step 2:-

   Rf= Cf*rSV2

   Rr= Cr*rSV2

Step 3:-

     Total resistance=Residual resistance + Frictional resistance

Step 4:-

     Plot resistance curves vs velocity

  Effective Power = TOTAL RESISTANCE X VELOCITY OF SHIP 

Resistance Curves:-


         To Conclude, Engine must be designed such that it must be able to overcome the Resistance


Comments

Post a Comment

Popular posts from this blog

OCTAHEDRAL SHEARING STRESS THEORY

-
Image
OCTAHEDRAL SHEARING STRESS THEORY                       According to this theory, the critical quantity is the shearing stress on the octahedral plane. The plane which is equally inclined to all the three principle axes is called the octahedral plane. τ oct = (1/3) [(σ 1 – σ 2 ) 2 + (σ 2 – σ 3 ) 2 + (σ 3 – σ 1 ) 2 ] 1/2                                                                                        where, τ oct = octahedral shearing stress Failure is said to occur when τ oct = ((√2)/3) σ e            This theory holds feasible for ductile materials and is similar to Von Mises theory.
Read more

WELD SYMBOLS USED IN DESIGN

-
Image
WELDING SYMBOLS AND ITS MEANING USED IN DESIGN                                 It’s a very usual aspect to use weld symbols in most of the mechanical drawings. Nowadays, it has become very important to have knowledge concerned with the welding symbols. There is a basic format given for showing the weld types used with its specifications. The welding standards have been varying in different areas. These standards had been updated from time to time by various non-profit organizations like AISC (American Institute of Steel Construction), API (American Petroleum Institute), AWS (American Welding Society) in USA and many other countries. In India, the welding standards are summarized by BIS (Bureau of Indian Standards) in which they are having certain IS (Indian standards) numbers or codes which are followed by most of the Indian companies.                        The above fig. shows the format used for annotation of weld symbol
Read more

GUEST’s or TRESCA’s THEORY

-
MAXIMUM SHEAR STRESS THEORY (GUEST’s or TRESCA’s THEORY)                  According to this theory, the elastic failure occurs when the greatest shear stress reaches a value equal to the shear stress at elastic limit in a simple tension test. This theory is considered for ductile materials, since shearing doesn’t occur in brittle materials. (½)(σ 1 – σ 3 ) = (½)σ e           or                                                               σ 1 – σ 3     =       σ e                   The maximum shear stress theory is also known as Guest’s or Tresca’s theory.
Read more