### 1. Introduction

### 2. Experimental and Numerical Analysis Conditions

### 2.2 Experimental Conditions

*F*,

_{x}*F*) and ±10 N-m for moment (

_{y}*M*).

_{z}#### 2.2.1 Resistance test

*Vm*denotes the velocity used in each test and the CFD analysis.

#### 2.2.2 Static drift test

### 2.3 Numerical Analysis Conditions

*k*−

*ω*was used as the turbulence model. Table 6 shows the details of the numerical techniques applied to the analysis.

### 3. Comparison of Experimental and Numerical Results

### 3.1 Comparison of Resistance Test Results

*X′*), which is a dimensionless value of the measured resistance of 0.5

_{uu}*ρL*

^{2}

*U*

^{2}(where

*ρ*: fluid density,

*L*: length of the Manta-type UUV, and

*U*: fluid velocity).

*k*−

*ω*SST turbulence model of OpenFOAM used in this study tends to be estimated with a smaller force as the velocity increases, which needs to be studied further. Considering that this study aims to show the usefulness of CFD analysis in the motion of underwater vehicles, rather than its advancement, the obtained result is reliable.

### 3.2 Comparison of Static Drift Test Analysis

*ρL*

^{2}

*U*

^{2}and 0.5

*ρL*

^{2}

*U*

^{2}, respectively, to review the results.

#### 3.2.1 Surge force

*X*′ is significantly different from the experimental and Star-CCM+ results, but those for

_{ww}*X*′ and

_{uu}*X*′ are similar, indicating that the results are in good agreement.

_{uw}#### 3.2.2 Heave force

*Z*′ was different from the experimental and Star-CCM+ results, while those for the other hydrodynamic derivatives agreed well.

_{ww}#### 3.2.3 Pitch moment

*M*

_{w}_{|}

_{w}_{|}′, shows a huge difference as the value of the pitch moment is much smaller than that of the heave force in terms of the size of the hydrodynamic force. In addition, as the hydrodynamic derivatives obtained from the OpenFOAM results shown in Table 15 are calculated only under some conditions, the result for

*M*′ is considerably different from the experimental and Star-CCM+ results, while the results for other hydrodynamic derivatives are in good agreement.

_{ww}### 4. Conclusion

The model test and CFD results showed a similar tendency for resistance by velocity.

In the static drift test, as a result of obtaining the hydrodynamic forces from each part of the Manta-type UUV model in CFD, the surge force acting on the hull, excluding the wings, changed depending on the direction of the drift angle, showing an asymmetric tendency. In addition, for the heave force and pitch moment, the same heave force acted on the vertical wing regardless of the direction of the drift angle, and the heave force and pitch moment occurred at a drift angle of 0°.

The model test and CFD analysis were conducted simultaneously, and the study was conducted without knowing the results. As shown in the results, the differences between the results obtained by different CFD solvers were rather insignificant and mutually reliable.