FIR analysis

Hull Roughness vs Ship Performance

CMP has been conducting collaboration study on fluid dynamics with Tokyo University of Science, Tokyo University of Agriculture and Technology, Kobe university and National Institute of Maritime Port and Aviation Technology (MPAT), National Maritime Research Institute (NMRI).

Next-Generation Marine Environment-related Technology Development Support Project.

In the joint research theme with the Class NK and the program supported by the Ministry of Land, Infrastructure, Transport and Tourism of Japan (MLIT), CMP has developed a ν-FIR Theory, 3D Hull roughness analyzer and Low friction AF.

FIR Theory

With FIR theory, the Friction Resistance can be estimated by measuring and evaluating roughness (Rz) and Wavelength (RSm) of paint surface using Double Cylinder Friction Resistance test developed by Tokyo University of Science.

3D Hull Roughness Analyzer

CMP developed a Portable 3D hull roughness analyzer which can measure values (Rz, Rc and RSm) on actual shipbuilding sites.

Introduction

Making the report

Introduction

Making the report

FIR calculation using speed and viscosity factors

Fluid dynamic study conducted by CMP suggests relations among roughness, wavelength, and viscous sublayer (as a speed and viscosity factor). Frontal projected area of roughness A exposed to outer layer of viscous sublayer is calculated using average roughness(Rc), wavelength(RSm) and viscous sublayer thickness(δs).

Roughness Allowance(ΔCF) can be calculated using the projected area A and a roughness resistance coefficient Croughness obtained from friction resistance test.

Effective Horse Power (EHP ) can be calculated using other factors (CW, CF, K, ρ, S, and V ).

Within the viscous sublayer roughness never influences the friction resistance. Viscous sublayer’ s thickness is changed by ship speed.

Hull roughness effect estimation program by HOPE Light (NMRI)

CMP and MPAT developed a hull roughness effect estimation program, which is based on ν-FIR theory and ship design support software HOPE Light (NMRI).


Heavy Barnacle


Slime

Direct Numerical Simulation (DNS)

  • DNS on 3D wavy roughness
  •  1. Long wavelength
  •  2. Short wavelength
  • By Tokyo University of Agriculture and Technology

Velocity profile measurement near the roughness by LDV measurement in cavitation tunnel. (NMRI)

14m flat plate test in 400m towing tank (NMRI)

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