Quiet Product Design

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1 Quiet Product Design Group Leader: Dr. Gary Koopmann Faculty Affiliates: Dr. Ashok Belegundu Dr. Weicheng Chen Dr. Chris Rahn Graduate Students: Rebecca Buxton Masters (ME) Lee Gorny PhD Yongsin Hwang PhD Andrew Kankey PhD Visitor: Ignazio Dimino Visiting Scholar Vibro-acoustics and Smart Structures Laboratory CIRA

2 A Wave Superposition Method Formulated in Digital Acoustic Space Dr. Yongsin Hwang

3 WAVE SUPERPOSITION METHOD REVIEW Method of Superposition n Center for Acoustics and Vibration 3

4 WAVE SUPERPOSITION METHOD REVIEW Method of Wave Superposition In summary Pressure : Surface velocity : N p g s 1 N u g s 1 Defining Impedance : Z g g 1 Gives: N p Z u 1 Center for Acoustics and Vibration 4

5 WAVE SUPERPOSITION METHOD REVIEW Discrete Power Calculation In summary Substituting p Z u with N v 1 av 1 2 N 1 Re N u * Z u v 1 Then av 1 2 N 1 N v 1 Re u * Z u Center for Acoustics and Vibration 5

6 MOTIVATION Difficulties associated with Meshing In a typical Mesh generation, many restrictions are imposed Center for Acoustics and Vibration 6

7 MOTIVATION easy adaptation Applying changes on a shape is easy with voxels Center for Acoustics and Vibration 7

8 VOXELIZATION Advantages of Voxel Volume representation Any 3D data set - each voxel can have different transparency Center for Acoustics and Vibration 8

9 VOXELIZATION Voxel versus Boundary Representation Voxels are easier to build and guaranty equal node area for faster computation time B-Rep can represent a shape better but elements do not necessarily have an equal area Center for Acoustics and Vibration 9

10 VOXELIZATION Voxelization technique To determine the right voxels Use Threshold, t sphere for dot cylinder for line t box for plane t t Center for Acoustics and Vibration 1

11 VOXELIZATION Voxelization technique (cont ) Two approaches are possible Voxelize Mesh elements If mesh is available one can voxelize piece-wise Voxelize from analytic description Can be done fast For surface voxelization, curved shape needs to be broken up(voxels are not uniform in all direction) Center for Acoustics and Vibration 11

12 VOXELIZATION Voxelization - Common technique Center for Acoustics and Vibration 12

13 VOXELIZATION Digital Acoustic Space Method Step 1. Define surface by finding active voxels Step 2. Import normals from geometry Step 3. Superposition Center for Acoustics and Vibration 13

14 IMPLEMENTATION OF VOXELS Volume velocity adjustment Voxel representation lose its accuracy in volume velocity calculation Matching volume velocity is necessary Length of black line and red line are not equal Translates to different surface area in 3D Center for Acoustics and Vibration 14

15 RESULTS voxelized using Sphere mesh Center for Acoustics and Vibration 15

16 RESULTS voxelized from analytic description r Center for Acoustics and Vibration 16

17 Power in db (re 1-12 W) Error in db RESULTS radially pulsating sphere Radiated Power ka, a=.4m ka, a=.4m Center for Acoustics and Vibration 17

18 RESULTS Cylinder, voxelized from mesh Center for Acoustics and Vibration 18

19 Power in db (re 1-12 W) Error in db RESULTS Frequency sweep of Breathing mode Radiated Power db difference between Power and Digital Acoustic Space Method Frequency (Hz) Frequency (Hz) Center for Acoustics and Vibration 19

20 Power in db (re 1-12 W) db difference RESULTS Frequency sweep of Mode 1,8 Radiated Power Radiated Power from 1,8 Mode Frequency (Hz) db difference between Power and Digital Acoustic Space Method Center for Acoustics and Vibration 2

21 Power in db (re 1-12 W) db difference RESULTS Frequency sweep of Mode 2,1 Radiated Power from 2,1 Mode Frequency (Hz) Center for Acoustics and Vibration 21

22 SENSITIVITY Sensitivity Study setup Center for Acoustics and Vibration 22

23 Power in Watts (W) SENSITIVITY Sensitivity Study General rule of 6 elements per wavelength is minimum requirement Radiated Power from Pulsating Box ka, a=1m Center for Acoustics and Vibration 23

24 CONCLUSION Summary Digital Acoustic Space Method easily accommodates shape changes on acoustic radiators Demonstrated Validity of Digital Acoustic Space Method on simple and complex geometries with complex mode shapes If active voxels are properly determined Matching volume velocity is the key to accurate analysis Sensitivity showed minimum requirement of 6 elements per acoustic wavelength Complexity study has shown minimal reduction of computational time Center for Acoustics and Vibration 24

25 Focusing Sound in Harbor Environments as a Swimmer Deterrent Andrew T. Kankey PSU/CAV Gary H. Koopmann PSU/CAV Chris D. Rahn PSU/CAV David L. Bradley PSU/ARL Kyle M. Becker PSU/ARL Low Frequency Sources

26 Low frequency sound can be steered and used as a non-lethal deterrent underwater Target In air (Broner, 1978), In water (Martin, et al, 25) Source Array

27 Current array focusing techniques need to be improved for shallow water environments Classic Array (Time Delay) Beam Forming doesn t take into account: 2 f d c sin variable sound speed variation in sources and spacing reflections from boundaries ϕ = θ d ϕ 1 =ϕ d ϕ 2 =2ϕ d ϕ 3 =3ϕ

28 Optimal Phase Search (OPS) Pressure Pressure 36 Phase 36 Phase Take data for all hydrophones at the same time to create a look up table for the optimal phases.

29 Pressure Level (db re 1 upa) Pressure Level (db re 1 upa) Numerical study shows a 12 db increase in pressure with OPS method near a boundary source 2 source Phase (degrees) source 2 source Phase (degrees) Phase of Source 2 (rads) Phase of Source 3 (rads) SPL (db re 1 upa) no reflec./reflec. Array Theory / 44 OPS Method no reflection OPS Method reflection / ~ ~ / 56

30 Coddington Cove, Newport, RI June 28 H1 ~325 m H2 H9 H3 H4H5 H8 H6 H7 mean water depth = 11 m silts, sandy silts, and clay sources 2 m from bottom Source Array ~18 m USS Forrestal USS Saratoga

31 Acoustic Source Array 7.4 m (24.3 feet) spacing J-15(3) HLF-1D Four J-15(3) s Three HLF-1D s

33 Phase (degrees) OPS method (green) agrees with classic array theory (black) in this harbor 45 Phasing for HLF1 Source #2, 1Hz HLF Setup S1 S2 S3 4 Pier Hydrophone

34 SPL (db re 1uPa) Pressures at each hydrophone are similar between the two methods. 164 SPL for HLF Source Array: Optimal and Theory, 1 Hz db 161 Morning Afternoon Hydrophone Array theory (dashed) and optimal phases (solid) were used.

35 Numerical modeling (FEM) of a harbor may be necessary when interrogation is unavailable

36 Bottom reflection coefficient can be numerically approximated using available data Reflection Coefficient - Coddington Cove - 2 layer over halfspace real imag R Z Z 2 2 Z Z 1 1 Calculated from data = c/z - Coddington Cove - 2 layer over halfspace real imag grazing angle (degrees) 1 1c Z Used in FEM code R R grazing angle (degrees)

37 β can be approximated by a constant at small distances from the source, a slope at larger ' Z θg horizontal distance 1 1c Z c sin g 1 R R R sin R c1 Z 1 g -.5 ρ1c Z2 = c/z - Coddington Cove - 2 layer over halfspace Distance of Interest horizontal distance (m) real imag

38 TL at 5m deep(db) TL at source depth (db) Using the slope approximation and the grazing angle correction, results meet expectations FEM - sin( g ) 3 2 FEM - sloped FEM - combined spherical 1 intermediate cylindrical Horizontal Distance (meters)

39 TL at 5m deep(db) TL at source depth (db) Using β leads to results that are in the same range as experimental data FEM - combined spherical intermediate cylindrical Horizontal Distance (meters)

40 Phase (degrees) Conclusions Summary Phasing for J15 Source #3, 1 Hz Hydrophone

41 Effects of Porous Sea Bottoms on the Propagation of Underwater Shock (UNDEX) Waves Using the P-α Equation of State Rebecca Buxton MS Thesis Mechanical Engineering Penn State April 22, 29 Shock test of Ex-USS Saipan plume shot. Photo by Rebecca Buxton, NSWC Carderock Division.

42 The goal of this talk is to provide a background, explain the work done, and provide a discussion of the results involved in this work Shock test of Ex-USS Saipan plume shot. Photo by Rebecca Buxton, NSWC Carderock Division. What are the motivations behind this work, and what has already been done? What is the P-α equation of state, how is it included in DYSMAS, and how is the model set up? 42 What are the results, and why do they matter?

43 Pressure, MPa What happens during an underwater shock event, and how does it affect water pressures? Bubble Time, msec [1] Direct loading [2] Surface reflection [3] Bottom reflection

Other research has focused on shock reflections in air or acoustic characterization underwater Shock in Air Linear Characterization in Water Numerical Modeling: Wang, et al.

44 Other research has focused on shock reflections in air or acoustic characterization underwater Shock in Air Linear Characterization in Water Numerical Modeling: Wang, et al. (24) Physical Testing: Attenborough, et al (24) Standley, et al. (22) Numerical Modeling: Liu, et al. (22) Stoll, Kan (21) Physical Testing: Kim, et al. (24) Richardson, et al. (23) Richardson, et al. (22) Walter (1998) Walter, et al. (1998) 44

45 Previous work with shocks in air Numerical Modeling: Modeled the three component elements of sand: grain, water, and air Showed that pore collapse is the first compression mechanism followed by the structural compression Physical Testing: Driven by a desire to quiet military equipment Demonstrated that placing a bed of granular material below a blast is effective for the reduction of blast sound Showed with a shock tube setup that soft foams were the most effective material shock absorption 45

Previous underwater sediment acoustic characterization Physical Testing: Core Numerical samples Modeling:

with water (no air) Bay Sound inclusions speed, or density, as introduced grain size, statistical porosity,

com/26- and Both acoustic modeling attenuation techniques are among led to weaker properties reflections of

jpg Central from a database corresponding of properties: solid material Acoustic sediment classifier system

fishing-pics.com/blog/media/1/25123- eel-river.jpg Eel River (CA) http://www.dailypress.

46 Previous underwater sediment acoustic characterization Physical Testing: Core Numerical samples Modeling: and situ testing conducted (good Modeled the sediment Chesapeake correlation) as a Gulf skeleton of Mexico with water (no air) Bay Sound inclusions speed, or density, as introduced grain size, statistical porosity, variability bulk density, dtypeid=4 and Both acoustic modeling attenuation techniques are among led to weaker properties reflections of interest than 1/Chesapeake+Bay_+Maryland.jpg Central from a database corresponding of properties: solid material Acoustic sediment classifier system (ASCS) Methane bubbles in the Eckernförde Bay showed a striking effect on acoustic properties eel-river.jpg Eel River (CA) 6-7/ jpg Dry Tortugas (FL) kernfoerdeluftbild1.jpg Eckernförde Bay 46 Locations of acoustic sediment on site testing

DYSMAS (Dynamic System Mechanics Advanced Simulation) is a navy fluid-solid coupling code used to simulate underwater explosions An explosive detonation and propagation simulated in water solved with

47 DYSMAS (Dynamic System Mechanics Advanced Simulation) is a navy fluid-solid coupling code used to simulate underwater explosions An explosive detonation and propagation simulated in water solved with the Gemini code (Eulerian) Fluid (Eulerian) and structural (Lagrangian) models are coupled allowing the explosiveexcited water load the solid model A solid model of a ship created in a solid modeling program and converted with preprocessor DYSMAS-P (Lagrangian) 47

48 To explore reflections of UNDEX waves from a bottom surface, a model field is created in Gemini Air Charge Water Sand 48 1) A regular mesh grid is established 2) Boundary and symmetry conditions are assigned 3) Materials are assigned to area of the grid

49 Each material (TNT, air water and sand) is modeled by an equation of state (EOS) Gamma Law EOS Tillotson EOS Air Charge Explosive (solid) Water Explosive (burn) 49 Mie-Grüeneisen EOS P-α EOS Sand

50 Sand is composed on multiple parts and can be modeled two ways in Gemini 5 Sand Grains Water Air Mie-Grüeneisen EOS Models the combined properties of the water and grains (solid) Need to specify mixture properties like density, internal energy, sound speed, shock vs. particle velocity slope, and Grüeneisen constant (tabulated) P-α EOS Allows for incorporation of air content through specification of porosity (α) Porosity is given by the ratio of solid density to porous density (α=ρs/ρ) Under loading, the material plastically deforms until a critical level is reached (α=1) Above the critical level, the solid sand is modeled by the Mie- Grüeneisen EOS

51 Pressure The P-α EOS is given by pressure as a function of porosity in this schematic ps: pressure for all pore collapse and transition to solid (Mie-Grüeneisen EOS) pe: pressure for plastic compression (zero for sand; no elastic cell wall compaction αp: porosity for plastic deformation (initial porosity for sand) α=1: full porous compaction (Mie-Grüeneisen EOS) 51 α 1) Initial state of sand 2) Unloading without reaching critical pressure 3) Full loading to critical pressure Herrmann (1968)

52 Test cases were chosen to hit critical points on the P-α curve and a spread of porosities 5% air.9% air Purely reflective 52

53 A pressure field animation from a case with a rigid bottom pure reflections behavior 53 Text box

54 The same pressure field animation with a porous bottom shows different reflection characteristics 54

55 Pressure and impulse were calculated for an array of points in the water and sand regions Air Water 1 cm Sand 2 cm 4 cm 6 cm 1 cm Red dotted lines: All measurement points (33 points in each plane) Blue stars: Selected points for graphical analysis

Pressure, D 8 1cm Sand pressure records show differences in 6 p shock s 4 wave propagation speed and attenuation 2.5 1 1.5 2 Time, msec α=1.9 with porosity α=1.

56 Pressure, D 8 1cm Sand pressure records show differences in 6 p shock s 4 wave propagation speed and attenuation Time, msec α=1.9 with porosity α=1.52 Pressure, Dynes/cm 2 16 x =1.9 In water 6cm depth 5cm 4cm 3cm 2cm 1cm 1cm p s Pressure, Dynes/cm 2 16 x =1.5 In water 6cm depth 5cm 4cm 3cm 2cm 1cm 1cm p s Time, msec Complete compaction Time, msec

57 Pressure, Dynes/cm 2 Sand pressures for each charge size (location on the P-α loading curve) for the higher porosity sand Complete, immediate compaction at all depths 16 x =1.5 In water 6cm depth 5cm 4cm 3cm 2cm 1cm 1cm p s Pressure, Dynes/cm 2 6 x Complete compaction at shallow depths only =1.5 In water 6cm depth 5cm 4cm 3cm 2cm 1cm 1cm p s Pressure, Dynes/cm 2 1 x Incomplete compaction =1.5 In water 6cm depth 5cm 4cm 3cm 2cm 1cm 1cm p s Time, msec 16 x 18 = kg TNT Charge In water 6cm depth Time, msec 1 kg TNT Charge 6 x 18 =1.9 In water Time, msec 5 g TNT Charge 1 x 17 =1.9 In water

58 Pressure, MPa Pressure, MPa Pressure, MPa Pressure, MPa Peak pressures in the porous cases decrease more substantially with distance from the charge cm Plane, Near Sand 1k, 1m, rigid 1k, 1m, =1.5 1k, 1m, = cm Plane, Near Sand 1k, 1m, rigid 1k, 1m, =1.5 1k, 1m, =1.9 A i r Time, msec Time, msec cm Plane, Near Sand 1k, 1m, rigid 1k, 1m, =1.5 1k, 1m, = cm Plane, Near Sand 1k, 1m, rigid 1k, 1m, =1.5 1k, 1m, = Time, msec Time, msec

59 Pressure, MPa Pressure, MPa Pressure, db re 1 Pa Pressure, db re MPa 1 Pa 15 The result of pressure reflections differs with water depth 4cm Plane, Near Sand 1k, 1m, rigid 1k, 1m, =1.9 1k, 1m, = cm Plane, 4cm Charge Plane, Depth Near Sand 1k, 1m, 1k, rigid 1m, rigid 1k, 1m, 1k, =1.9 1m, =1.9 1k, 1m, 1k, =1.5 1m, = cm Plane, Near Charge Surface Depth 1k, 1m, rigid 1k, 1m, =1.9 1k, 1m, =1.5 1 A i r A i r A i r Time, msec Time, msec Time, msec Time, msec 59 Time delay of the reflected peak decreases with depth Raised pressures after the initial peak near the sand

60 ater depth, cm Water depth, cm Peak pressures are plotted at the four vertical Horizontal distance from charge, cm measurement planes throughout the water Peak Pressures, MPa(x5)for 1 kg charge Rigid =1.9 = Horizontal distance from charge, cm Peak Pressures, MPa(x15)for 5 g charge the porous cases and at the bottom surface for the rigid Rigid case -5 =1.9 Pressures -1 for the porous cases are at a minimum at the = MPa 2MPa 2MPa 2MPa Maximum pressures are seen at charge depth for both of water-air and water-sand interface for the porous cases

61 Plotting db pressures (re 1μPa) show elevated pressures out in time that a peak value does not capture Pressure, MPa Pressure, db re 1 Pa 15 4cm Plane, Near Sand 1k, 1m, rigid 1k, 1m, =1.9 1k, 1m, = cm Plane, Near Sand 1k, 1m, rigid 1k, 1m, =1.9 1k, 1m, = Time, msec Time, msec 61 While peak pressure is one indicator shock and damage potential it does not tell the whole story

62 , MPa, MPa sity, MPa*s Pressure, MPa Pressure, MPa Impulse Intensity, MPa*s Impulse intensity is the time integral of pressure variation and an indicator of structural damage cm Plane, Near Sand 1k, 1m, rigid 1k, 1m, =1.5 1k, 1m, = cm Plane, Near Sand 7 x 1-3 2cm Plane, Near Sand k, 1m, 1k, rigid 1m, rigid 1k, 1m, 1k, 1m, =1.5 =1.5 1k, 1m, 1k, 1m, =1.9 = Time, msec Time, Time, msec msec cm Plane, Near Sand I t 2 1k, 1m, rigid 1k, 1m, =1.5 t1 1k, 1m, =1.9 ( p( t) cm Plane, Near Sand 2.5 x 1-3 6cm Plane, Near Sand p ambient ) dt 1k, 1m, 1k, rigid 1m, rigid 1k, 1m, 1k, 1m, =1.5 =1.5 1k, 1m, 1k, 1m, =1.9 =1.9

I*R I*R 6cm plane 6cm plane Collapsing impulse intensities (using time delay 1cm plane 1cm plane and -1 spreading compensation) -1 indicates energy 1 2 3 4 5 1 2 3 4 5 t/(r/c) absorption in the sand

63 I*R I*R 6cm plane 6cm plane Collapsing impulse intensities (using time delay 1cm plane 1cm plane and -1 spreading compensation) -1 indicates energy t/(r/c) absorption in the sand t/(r/c) 5 1kg charge, near sand, rigid 5 1kg charge, near sand,, alpha= A i r cm plane 4cm plane 6cm plane 1cm plane t/(r/c) The rigid case collapses well with similar peak and plateau values 1 2cm plane 4cm plane 6cm plane 1cm plane t/(r/c) The porous case shows drops in peak impulse intensity and its plateau value

64 For a direct comparison of each porosity to the reference rigid condition, db reductions were calculated referenced to the rigid value pdb reduction 2 log 1 p porous,max p rigid,max IdB reduction 2 log 1 I I porous, max rigid, max 64 The maximum pressure and impulse intensity values are calculated for each selected point in the pressure field (for each bottom condition and charge size) The values for the two porous conditions are used to find db reductions referenced to the corresponding rigid case value The resulting values are then displayed to show variation in reduction over the water field

65 ter depth, cm Water depth, cm W -25 Differences in porosity have little effect on peak pressure reduction Horizontal distance over from charge, the cm rigid case kg Charge Rigid Peak Pressure-Normalized db Peak Pressure Reductions(x1) 5dB 5dB 5dB 5dB =1.5 = Horizontal distance from charge, cm Porosity 5g differences Charge Rigid Peak have Pressure-Normalized minimal effect db Peak Pressure Reductions(x1) Porosity, in itself, affects a region close to the water-sand interface =1.5 The -5 height of the effected region increases with distance from the =1.9 charge The reduction increases slightly with charge size (other charge sizes shown in thesis) -1-15

66 Water depth, cm Water depth, cm W -25 Higher -3 porosity leads to greater reductions in maximum Horizontal impulse distance from charge, intensity cm kg Charge Rigid Peak Impsule-Normalized db Peak Impulse Reductions(x1) 5dB 5dB 5dB 5dB Horizontal distance from charge, cm =1.5 = Porosity differences 5g Charge Rigid Peak have Impsule-Normalized greatest effect db Peak near Impulse water-sand Reductions(x1) interface =1.5-5 interface =1.9 Maximum reductions (for both porosities) greatest near water-sand The height above the sand where reduction varies with porosity decreases with increasing distance from the charge Relative reductions increase slightly with a decrease in charge size (other charge sizes not shown in thesis)

67 Future work on this topic is divided between more modeling and physical testing Continued Modeling Physical Testing 67 Model stratified sea bottoms to more accurately match real-world conditions Investigate the importance of shear in sand modeling in shock circumstances Place a structural model (ship, sub, plate, simple pressure vessel, etc.) in the water field and look at its physical properties (deformation, acceleration, etc.) The P- α EOS in DYSMAS has never been directly validated for the water field from a reflected shock Create the exact geometries, charges and instrumentation locations used for this computational work Use Hopkinson ( cube root ) scaling to correlate results with scaled testing -since P-α does not use grain size as a parameter, length scaling of sand particles is unnecessary

In summary, the modeling effort showed the effects of a shock reflecting off of a porous sea bottom Impulse intensities show energy loss with a porous sea bottom Higher porosities show higher

68 In summary, the modeling effort showed the effects of a shock reflecting off of a porous sea bottom Impulse intensities show energy loss with a porous sea bottom Higher porosities show higher reductions in max impulse intensity Region of reduction concentrated near watersand interface In Changes the sand: in porosity do not Higher affect peak porosities pressure lead to slower Porosity shock in itself speed does and more reduce rapid pressures peak attenuation over the Higher rigid case porosities near the lead watersand interface reflective wave to tensile behavior in the water 68 Questions?

69 Summary of effects of porosity (sand proportion, pressure and II) Changes in porosity, α, have negligible effect on peak pressure at any point in the water field 69 Porosity itself does reduce peak pressures, most dramatically at the water-sand interface, and is limited to the region near the bottom of the water field. Impulse intensity histories show loss in the water field due to the presence of a porous bottom condition (higher porosities, higher losses) Reductions in peak impulse intensity with an increase in porosity are limited to the region near the water-sand interface. Increase in porosity and decrease in the pressure incident on the water-sand interface increase the presence of a tensile reflected wave leading to low local water pressures.

Shock factor investigation in a 3-D finite element model under shock loading

10(2013) 941 952 Shock factor investigation in a 3-D finite element model under shock loading Abstract In this paper, a scaled 3D ship under shock loading is modeled and analyzed by finite element method.