ASME V & V Symposium, May, 2012

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1 ASME V & V Symposium, May, 2012 SBIR N07-098: Fire Integrity in Advanced Ship Structures Dr. Dave Keyser Fellow, ASME dave.keyser@survice.com Mark Butkiewicz mark.butkiewicz@survice.com Dave Hall dave.hall@survice.com

2 Project Goal Apollo TM Develop integrated software for engineers and shipbuilders to predict the strength-degradation of composite structural members during and after exposure to fires 2

Introduction of Apollo Provides modern, flexible computing structure Dynamic/adaptable Eulerian and Lagrangian grids Easily tie into existing Finite Element Analysis (FEA) codes for

3 Introduction of Apollo Provides modern, flexible computing structure Dynamic/adaptable Eulerian and Lagrangian grids Easily tie into existing Finite Element Analysis (FEA) codes for modeling structural response Eulerian CFD (Flow Field) Grid Dynamic and Adaptable Grid Eulerian/Lagrangian Grid Interface Apollo Grid Apollo core structure developed under SURVICE IR&D 3

4 Apollo CFD Fundamentals Apollo TM uses the same three fundamental concepts as all Computational Fluid Dynamics (CFD) codes: Conservation of Mass Conservation of Momentum Conservation of Energy However, Apollo uses them differently: applying Control Volume Integrals, vice partial differential equations: Conservation of Mass is effected via Conservation of Species Each mole of each substance is tracked through the space Needed for combustion reactions and tracking products of combustion Conservation of Momentum is computed directly Conservation of Energy includes: Kinetic energy Enthalpy Gravitational Potential Energy 4

5 Conservation of Momentum We begin with the conservation of momentum: t gρdxdydz = V( p da + F + ) surface vol surface volume pdxdydz when discretized becomes: 6 s da g 7 n MW dxdydz + jj i i jk cs= 1 1 cs= 1 cs= 1 6 s da + 6 p( V da) = t [ pdxdydz] Where n i is the number of moles of species i per unit volume, and p is the momentum per unit volume, and the s jj & jk are the stresses on the surface of the cell. 5

6 Conservation of Mass and Species Conservation of Mass and Species: surface p da = t vol ρdxdydz 6 cs= 1 p daδt = nimwidxdydz t t + δ i i n MW dxdydz i i t Where n i = the number of moles of species i per unit volume. Presently we have 6 species: Oxygen, Nitrogen, Fuel Vapor, Carbon Dioxide, Water Vapor, and Carbon (soot) These can be augmented easily as the application requires. 6

7 Conservation of Energy Conservation of energy (e) is defined as the energy per unit mass, which is the sum of the kinetic energy, the gravitational potential energy, and the enthalpy. Enthalpy, h, is the sum of the internal thermal energy and stored elastic energy: 2 V sii e = + g + u( T ) +, where : u = C pt, and : h = u + 2 ρ Then, the rate of change of energy inside each cell equals the heat added by combustion and the net flux of energy through the surface: 6 t Q t ( eρdxdydz) = + eρv Multiplying by the time step and discretizing: 1 n da ( V da) δt + δq = eρdxdydz t+ δt eρdxdydz t = eρ e( p da) δt + δq cs n cs sii ρ 7

8 The Joint DoD Validation Process The DoD V&V Process is described in MIL-STD

9 Validation of High-Pressure Steam Flow in Performance Test Code Measurement These are Primarily used in Multi-megawatt Electric- Power Plants: Performance Tests & Regulatory Power Monitoring of both Nuclear and Fossil-fueled Plants High Pressure and High Temperature Steam Flow: Pressure = 12,592.5 kpa Density = kg/m 3 Temperature = K Uniform Inlet Velocity = m/s Absolute viscosity = 2.68 x 10-5 Pa-s Throat Reynolds No. = x 10 6 Reference Flow Standard: ASME PTC 19.5, Flow Measurement, Section 5 The flow equation is based on the Bernoulli equation for compressible flow, and its calculated result is modified by a semi-empirical Coefficient of Discharge derived from boundary layer theory and a half-century of laboratory test data 9

10 Theoretical Model of the ASME Nozzle The boundary layer causes the coefficient of discharge Flow Regime 10

Validation of High-Pressure Steam Flow Performance Test Code Measurement Verification & validation test case; ASME Throat Tap Nozzle The most accurate large-flow

3% Inlet D = 40 cm Nozzle throat, d = 20 cm Inlet uniform velocity = 9.83 m/s Fluid Properties: Density = 38.23 kg/cu. M. System Pressure = 126 bar Temp = 713.

11 Validation of High-Pressure Steam Flow Performance Test Code Measurement Verification & validation test case; ASME Throat Tap Nozzle The most accurate large-flow device used in Performance Test Codes on Steam Turbines Thousands Lab Calibration Data Decades of use, Coefficient of Discharge known + 0.3% Inlet D = 40 cm Nozzle throat, d = 20 cm Inlet uniform velocity = 9.83 m/s Fluid Properties: Density = kg/cu. M. System Pressure = 126 bar Temp = K Apollo TM CFD of Flow Model Nozzle V&V CFD Flow of Steam from Apollo Results: kg/s ASME mass flow vice from Apollo = kg/s (= 1/3% difference, equivalent to test data). 11

12 fd St = V 2 nd Validation Test: Vortex-Shedding The pioneering work was carried out by Vincenc Strouhal, a Czech physicist who published it in 1878 [1]. He investigated the relation between the tone of a singing wire and fluid velocity and found that the sound produced by the wire was directly related to the vortex-shedding frequency. The nondimensional analysis led to the dimensionless Strouhal number: Sr = fd / V Then Rayleigh [2] pointed out that the Strouhal number should be a function of the Reynolds number. 12

Historical Published Data -- Rayleigh Observations of Rayleigh show the variation of St versus Rd It shows a quite nonlinear curve which increases

13 Historical Published Data -- Rayleigh Observations of Rayleigh show the variation of St versus Rd It shows a quite nonlinear curve which increases significantly at higher Rd The following validation comparison for Apollo is in the rising portion of the curve at its upper Rd Region of Simulated Test 13

formation and growth of the vortices; consequently the beginning of the measurement period began at

14 Simulation Data Analysis The shedding frequency calculated by Apollo was determined by counting the passing vortices during the simulation s elapsed time The output showed the initial transient formation and growth of the vortices; consequently the beginning of the measurement period began at around 0.6 seconds when the oscillatory pattern appeared to be unchanging Von Karman Vortices Apollo Results 14

15 2 nd Validation Test-Vortex Shedding Observed Data of Vortex Periods Run # End Time, sec Start Time, sec Cycles Period sec Freq., Hz The mean observed frequency from the simulation is 26.2 Hz, and the uncertainty at the 95% confidence level is Hz 15

16 Empirical Experiments: Validation References CASE 1: Apollo vs. Rayleigh s data of a long cylinder in free stream In this case, the upstream, uniform velocity was used to calculate the Strouhal number, and the Reynolds number based on the diameter of the cylinder is: Rd = 1.4 x 10 6 The empirical Sr = 0.23, so the frequency = Hz The difference between Rayleigh s tests and Apollo TM is that our cylinder is not long nor is it in an atmospheric free stream The ceiling and floor of the conduit may attenuate the vortex waves by viscous friction. Hence, this condition likely forms a lower bound on the frequency 16

17 St V 0.24(13.11) f = = = Hz d 0.1 Empirical Experiments: Validation References CASE 2: Apollo vs. Rayleigh s data of a long cylinder in free stream In this case, accounting for the blockage of the conduit by the cylinder increases the velocity in the plane of the cylinder, since its presence reduces the area available to the flow, so: Rd = 1.87E06 St = 0.24 And the empirically predicted frequency becomes: f = St V =.24 x = Hz d 0.1 This velocity is determined from conservation of mass via the area ratio Therefore this value represents a kind of upper bound on the true value. 17

18 Vortex-Shedding Validation Results The midrange of the Upper and Lower Bounds found in reported tests = 27 Hz Which is 3% higher than 26.2 Hz observed from the simulations, And is well within the +0.9 Hz 2σ uncertainty of these observations Since the published references do not match the boundary conditions of the simulations precisely, some magnitude of differences need be expected 18

19 Uncertainty Analysis of the Vortex-Shedding The method for estimating the overall test uncertainty for the simulations and cases in this paper is that established by the ASME in their Performance Test Codes [3]. The accepted standard, reported value is that at the 95% confidence level. Sources of Uncertainty: The empirical uncertainty of the measurements of Strouhal number The observational uncertainty of Apollo s shedding frequency The measurement of velocity The measurement of the Reynolds number The readability of the data curve of Strouhal number The geometric dimensions of the bluff bodies and the conduits-- negligible 19

20 Uncertainty Analysis of the Vortex-Shedding Strouhal vs. Reynolds numbers for Oscillatory Flow in Ref. 5 The uncertainty bands shown for St are + 0.7% 20

21 Uncertainty Analysis of the Vortex-Shedding The random uncertainty of the observed Apollo frequencies as reported is + 3.4%. The reported uncertainty [5] in the velocity, and also the Rd, values is + 2.0% The systematic readability error of the reference curve of Figure 3 is ¼ of a division, which is ~St When these are combined IAW ASME PTC 19.1, Test Uncertainty The result at the 95% confidence level is ~+8.3% There is no statistically significant difference between the simulation of oscillatory flow computed by Apollo s CFD and the published, experimental results 21

Future Work 1. Run another simulation of vortex-shedding with another fluid at a lower Rd where the St/Rd curve is more constant. 2. Conduct some simulations of blast effects: 1.

22 Future Work 1. Run another simulation of vortex-shedding with another fluid at a lower Rd where the St/Rd curve is more constant. 2. Conduct some simulations of blast effects: 1. Since Apollo is based completely on the fundamentals of physics, it seems to simulate very rapid flows, acoustic waves, and blast fronts. 2. Validation will utilize a couple of USA blast codes as well as tests from the Aberdeen Proving Ground. Warhead Fragments Blast Wave Weapon Detonation 22

23 References and Bibliography [1] Strouhal, V. Ueber eine besondere Art der Tonerregung, Annalen der Physik und Chemie, 1878, 5 (10) (1878), [2] Rayleigh, L. The Theory of Sound, 1945 (Dover Publications, New York). [3] ASME Performance Test Code 19.1, Test Uncertainty [4] en.wikipedia.org/wiki/strouhal_number [5] SHI,L. YU, Z. and JAWORSKI, A.,Investigation into the Strouhal numbers associated with vortex shedding from parallel-plate thermoacoustic stacks in oscillatory flow conditions, School of Mechanical, Aerospace and Civil Engineering, University of Manchester, United Kingdom [6] van Dyke, M., An Album of Fluid Motion, The Parabolic Press, Stanford, CA, 1982 [7] Reference Flow Standard: ASME PTC 19.5, Flow Measurement, Section 5. 23

24 Fin 24

25 Cells in the Grid & Conservation Equations Memory management In the CFD computation, each cell is treated as a Control Volume having six sides and a miniature volume These cells are grouped into regions for efficient processing Minimize/eliminate missed cache events Region Internal cells guaranteed to be within on-chip memory cache Boundary cells require adjacent region to be loaded/locked in on-chip memory cache 25

CHAPTER (13) FLOW MEASUREMENTS

CHAPTER (13) FLOW MEASUREMENTS 09/12/2010 Dr. Munzer Ebaid 1 Instruments for the Measurements of Flow Rate 1. Direct Methods: Volume or weight measurements. 2. Indirect Methods: Venturi meters, Orifices