8/24/2014

1

Appendix III. CFDShip-Iowa Analysis of Onset and Separation of Instantaneous Vortical Structures, Instability

Analysis and Turbulence Budget for Static Drift Condition

Table III.1-1: Summary of additional instantaneous vortices, apart from the dominant mean vortices, predicted by CFDShip-Iowa V4 DES for DTMB 5415 with

bilge keels at 20 drift at Re = 5.13×106, Fr = 0.28

Flow side Vortex Onset Separation Progression

Leeward

Sonar

Dome

surface

Leading edge vortex,

LE-V

Leading edge

Vertically aligned in between free-surface

and sonar dome

Closed-type

Boundary layer separation Unsteady shedding by axial velocity

Leading edge

free-furface vortex

LE-FSV

Below the free-surface and close to the

leading edge

Circulation induced by the free-surface

Open-closed type

Boundary layer separation

Advected by the flow streamline

underneath the free-surface

Leading edge – Sonar dome

reconnection vortex

LE-SD-R

Separation on sonar dome surface close to

the leading edge (X = 0.008, Z = -0.04) and

slighty upstream (X = 0.03, Z = -0.043).

Closed-type, connects leading edge and sonar

dome separation

Both Boundary layer and cross flow separation

Needs investigation

Free-surface vortex

FSV

Free-surface induced

Aligned along axial direction in between

hull and breaking waves

Open-closed type

Boundary layer separation

Advected along the hull by axial velocity

and towards free-surface bt the SDTV

circulation

Sonar dome-hull

reconnection vortex

SD-H-R

Flow separation on concave surface of

sonar dome (X = 0.068, Z = -0.048) and on

the hull (X = X = 0.055, Z = -0.031)

Closed-type

Both Boundary layer and cross flow separation

Connects hull high pressure source and sonar

dome saddle point

Needs investigation

Fore body keel vortex

FBKV

Concave section of the sonar dome

X = 0.055, Z = -0.037

Free-surface induced downward flow and

upward flow from the concave portion of

sonar dome

Open-type

Boundary layer separation at the sonar dome-

keel intersection

Advected by streamwise velocity

Moves towards the hull due to

lifting generted by SDTV

Leeward bilge keel vortex,

BKV

Vortex separation behind blunt body due to

incoming cross flow

Multiple separations along the bilge keel

Open-type

Shear layer separation Advected by freestream velocity

8/24/2014

2

Table III.1-2: Vortices and scaling for DTMB 5415 with bilge keels at 20 drift simulation.

Vortex Instability type

Unsteadiness Measurement

Location Period Frequency (f) Length (L)

Velocity

(U) St=fL/U

Windward

side

BKTV Helical Points are shown in

Fig. III.1-13 Results shown in Fig. III.1-14

Bow free surface vortex

FSBW2

Plunging wave

breaking Analysis required

Shoulder free surface

vortex

Spilling wave

breaking Analysis Required

Leeward side

SDTV Helical Points are shown in

Fig. III.1-12 Results shown in Fig. III.1-14

LW-FBKV Shear-layer X=0.2, Y=-0.11, Z=-0.0436 0.0625-

0.0667 15.0-16.0 =1.89×10-4 1.02

0.0028-

0.0030

Leeward free surface

vortex FSBW1

Plunging

breaking wave X=0.16, Y=-0.158, Z=-0.0148

0.055-

0.067 14.93-18.18 1.00

Shoulder free surface

vortex FSBW3

Spilling wave

breaking Analysis Required

SDTV induced wave

breaking vortex FS3

Spilling wave

breaking Analysis Required

Leeward bilge keel vortex Analysis Required

Sonar dome separation

bubble

Shear-layer, BSL1 X=0.056, Y=-0.168, Z=-0.0327 0.0714 14.0 =4.23×10-4 1.03 0.0059

Shear-layer, BSL2 X=0.078, Y=-0.176, Z=-0.0513 0.0769-

0.0833 12.05 -13.00 =1.45×10-4 1.14

0.0015-

0.0017

Karman-like, BK X=0.088, Y=-0.168, Z=-0.0454 0.091 10.99 Half wake width

H=0.0144 1.20 0.132

Flapping-like Analysis Required

Transom Transom vortices Karman-like Analysis Required Half the distance between BSL1 and BSL2 instabilities.

8/24/2014

3

(a) 10 M grid URANS (b) 10M grid DES

(b) 48M grid DES (c) 250M grid DES

Figure III.1-1: Free-surface elevation contour obtained from (a) 10M grid URANS, (b) 10M grid DES, (c) 48M grid DES and (d) 250M grid DES. Contour levels

are from -0.01 to 0.01 with intervals of 4×10-4. Figure (a) shows the inset locations used in the figures below.

Inset A

Inset B

Inset C

Inset D

8/24/2014

4

(a)

(b)

Figure III.1-2: (a) View of the vortical structures (Q = 2000) on the leeward sonar dome surface. (b) Hull surface streamline for =20

case obtained using CFDShip-Iowa (DES, 10M) instantanesou solution.

Free-surface

Vortex, FSV

Open Separation

Line

Saddle point

Closed Separation

Open Separation

Line

Low pressure sink

High pressure source

Converging

streamlines

Converging

streamlines

Converging

streamlines Saddle point

Closed Separation

Sink

Leading Edge Free-

Surface Vortex

LE-FSV

Leading Edge Vortex,

LE-V

Leading edge – Sonar dome reconnection vortex

LE-SD-R

Sonar dome- Hull

reconnection vortex

SD-H-R

8/24/2014

5

Figure III.1-3: Vortices on the windward side are shown using Q = 300. Surface streamline on the windward sonar dome surface for

=20 case obtained using CFDShip-Iowa (DES, 10M) instantanesou solution.

8/24/2014

6

Figure III.1-4: Surface streamline on the leeward leading edge and Q=5000 showing the vortical structures for =20 case obtained

using CFDShip-Iowa (DES, 10M) instantanesou solution .

Leading Edge

Separation Line

Saddle point

Boundary layer separates

Flow-streamline

LE-FSV

LE-V

X=0.035 X=0.025

8/24/2014

7

(a)

(b)

Figure III.1-5: Flow streamline below the free-surface showing the generation of the LE-FSV for =20 case obtained using CFDShip-

Iowa (DES, 10M) instantanesou solution.

LE-FSV

8/24/2014

8

(a)

(b)

Figure III.1-6: (a) View of the LE-SD-R vortex using Q = 5000, flow streamline at Z = -0.043, and slice X = 0.03 shows the vortex

using Q = 10000 contours (red line). (b) Cross-flow recirculation associated with LE-SD-R vortex on the sonar dome for =20 case

obtained using CFDShip-Iowa (DES, 10M) instantanesou solution.

LE-SD-R

Z = -0.043

X=0.03 X=0.03 X=0.035 X=0.035

Z = -0.043

Z = -0.043

8/24/2014

9

Figure III.1-7: Shoulder free-surface vortex FSV is shown using Q = 2000. Slices Z = -0.021, X = 0.5 – 0.1 are shown to analyze the

generation of the vortex for =20 case obtained using CFDShip-Iowa (DES, 10M) instantanesou solution.

X=0.1 X=0.05

Z=-0.021

Z=-0.021

Free-surface

Vortex, FSV

8/24/2014

10

Figure III.1-8: Sonar dome –Hull reconnection vortex is shown by Q = 2000 for =20 case obtained using CFDShip-Iowa (DES, 10M)

instantanesou solution.

Sonar dome- Hull

reconnection vortex

SD-H-R

Z=-0.041

Connection on hull

8/24/2014

11

Inset A Inset B Inset C Inset D

(a) 10M grid, URANS

(b) 10M grid, DES

(c) 48M grid, DES

(d) 250M grid, DES

Fig. III.1-9: Wave breaking pattern predicted for obtained using CFDShip-Iowa on 10M, 48M and 250M grids. Inset A-D locations are shown in Fig. III.1-1.

Windward shoulder

breaking wave scar

Leeward shoulder

breaking wave scar

Sonar done vortex induced

breaking wave scar

Transom breaking wave scar

Leeward bow wave

breaking scars

Windward bow wave

breaking scar

8/24/2014

12

Fig. III.1-10: Leeward side view of the isosurfaces of Q=300 for an instantaneous solution T=7.5L/U using 10M grid. Isosurfaces are colored using pressure and

free-surface using z.

Sonar Dome Vortex

(SDTV)

Leeward Free-surface

Vortex (FSBW1)

LW-FBKV

Shear-layer

Instability (BSL1)

Shear-layer

Instability (BSL2)

Karman-like

Instability (BK)

X=0.088

Z=-0.04

X=0.088

Z=-0.04

BSL1

BSL2 BK

LW-BKV

Windward Fore-

body Keel Vortex

Leeward Fore-

body Keel Vortex

Transom vortices,

shown using Q = 100

8/24/2014

13

Fig. III.1-11: Windward side view of the isosurfaces of Q=300 for an instantaneous solution T=7.5L/U using 10M grid. Isosurfaces are colored using pressure

and free-surface using z.

Windward Free-surface Vortex (FSBW2)

Bilge keel

Tip Vortex (BKTV)

Leeward After-body keel

Vortex (ABKV)

Leeward SDTV induced free-

surface Vortex (FS3)

Windward After-body keel

Vortex (ABKV)

8/24/2014

14

Fig. III.1-12: Instantaneous solution streamlines at several X planes show the inception of SDTV at X=0.125, Y=-0.1434, Z=-0.0542 and advection on leeward side. Contours are for

pressure.

SDTV inception

X=0.20 X=0.16 X=0.13 X=0.125 X=0.12

P1

P2

P3

P4 P5

SDTV

8/24/2014

15

Fig. III.1-13: Instantaneous solution streamlines at several X planes show Bilge keel tip vortex (BKTV) formation at X=0.375, Y=0.00277, Z=-0.0339, which is advected to the port side.

Contours are for pressure.

X=0.375 X=0.6 X=0.75 X=0.85 X=1.0

BKTV

BKTV

P1

P3

P2

P4

P6

P5

8/24/2014

16

(a)

(b)

Fig. III.1-14: Variation of (a) dimensionless frequency and (b) product frequency and distance from origin as a function of stream wise distance along vortex core

for SDTV and BKTV.

8/24/2014

17

Fig. III.1-15: Slices of instantaneous flow field shows inception of BSL1 at X=0.056, Y=-0.168, Z=-0.0327 and BSL2 at X=0.078, Y=-0.176, Z=-0.0513. Counter

rotating KHB1 and KHB2 merge at shown at X=0.084 slice and are advected away from the sonar dome bulb as shown in X=0.092-0.1 slices. Contours are for

pressure.

X=0.056 X=0.078 X=0.084 X=0.088

X=0.092 X=0.096 X=0.1

Z=-0.04

Karman-like

Instability (BK) Shear-layer

Instability (BSL1)

Shear-layer

Instability (BSL2)

Shear-layer

Instability (BSL1)

Inception

(P1)

Shear-layer

Instability (BSL2)

Inception (P2)

BSL1

FSBW1

Karman-like

Instability (BK)

(P3)

Z=0.04

X=0.088

X=0.078 X=0.056

8/24/2014

18

(a) (b)

(c)

Fig. III.1-16: Dominant frequency for (a) BSL1, (b) BSL2 and (c) BK.

8/24/2014

19

(a)

(b)

Fig. III.1-17: (a) Instantaneous solution streamlines at several X planes show boundary layer flow separation at X=0.2, Y=-0.11, Z=-0.0436, which eventually forms KSL at X=0.6.

Contours are for pressure. (b) KSL dominant frequency.

X=0.2 X=0.3 X=0.4 X=0.5 X=0.6

KSL inception

(P4)

8/24/2014

20

(a)

(b)

Fig. III.1-18: (a) FSBW1 dominant frequency and (b) FSBW2 dominant frequency.

0

0.02

0.04

0.06

0.08

0.1

0 0.1 0.2 0.3 0.4

Am

pli

tud

e

Period

250M Grid

48M Grid

10M Grid

8/24/2014

21

(a) 10M Grid

BK

8/24/2014

22

(b) 48M Grid

Fig. III.1-19: TKE budget at x/L=0.1.

8/24/2014

23

(a) 10M Grid

SDTV KSL

8/24/2014

24

(b) 48M Grid

Fig. III.1-20: TKE budget at x/L=0.2.

8/24/2014

25

(a) 10M Grid

SDTV BKK

8/24/2014

26

(b) 48M Grid

Fig. III.1-21: TKE budget at x/L=0.4.

8/24/2014

27

(a) 10M Grid

SDTV

KSL BKK

8/24/2014

28

(b) 48M Grid

Fig. III.1-22: TKE budget at x/L=0.6.

8/24/2014

29

(a) 10M Grid

FS3

SDTV KTV

8/24/2014

30

(b) 48M Grid

Fig. III.1-23: TKE budget at x/L=0.8.

8/24/2014

31

(a) 10M Grid

KTV SDTV

8/24/2014

32

(b) 48M Grid

Fig. III.1-24: TKE budget at x/L=1.0.

8/24/2014

33

(a) 10M Grid

SDTV

KTV

8/24/2014

34

(b) 48M Grid

Fig. III.1-25: TKE budget at x/L=1.1.