Atle Jensen. Experiments on waves in oil and ice (WOICE) NFR Petromaks 2. Contributions from: Jean Rabault, Graig Sutherland and Petter Vollestad

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1 Atle Jensen Experiments on waves in oil and ice (WOICE) NFR Petromaks 2 Contributions from: Jean Rabault, Graig Sutherland and Petter Vollestad

2 Fluid mechanics - uio Mechanics (7 faculty + 5 adjunct and 16 PhD, 3 industrial PhD, 5 PD) Ocean waves, currents and tsunamis Fluid mechanics laboratory Multiphase flow and turbulence Marine hydrodynamics and coastal engineering Biomechanics Microfluidics Length scales from km to µm Study processes applied math partial differential equations Mechanics

3 Navier-Stokes; Momentum equation Velocity field u, Pressure field p Viscosity ν, density ρ (constants) External force f Condition: Mechanics

4 WOICE: Scope of project Study interaction between waves, oil and ice Waves damped by ice Energy exchange air/sea Turbulence in the ocean Wave damping > increased currents New insight - education Mechanics

5 Methods Theory, modeling and simulations Field measurements Experiments in the laboratory Close the gap between observations and theory Simplified models by laboratory simulations Mechanics

6 Wave theory Surface tension neglected (no ripples) Perfect fluid (no viscosity) Incompressible flow Irrotational flow u = 0 u = 0 or u = φ Laplace equation 2 φ = 0 Boundary conditions At the free-surface: p = p a At the bottom: u n = 0 (atmospheric pressure) (normal velocity is zero) Mechanics

7 Eulerian velocity (light blue) gives closed orbital velocities (no net transport, except above trough line) Lagrangian velocity (red, yellow and purple) surf" with the wave (net transport) Mean drift in the direction of wave propagation is called the Stokes drift Primarily conned to the surface Important for material transport at the surface Mechanics

8 Theoretical Damping with a Surface Cover a 0 cover a 0 e x Surface cover leads to a decrease in momentum This must be conserved -> mean current E 1/2ρga 2 M = E/cp cp ω/k Mechanics

9 Mechanics

10 Hydrodynamics lab, UiO Mechanics

11 Experiments Effect of elastic cover on waves; Measurements of particle velocities and mean drift Mechanics

12 Velocity profiles, with and without cover, f=2.0hz Mechanics

13 What is turbulence Unsteady, aperiodic motion in which all three velocity components fluctuate, mixing matter, momentum, and energy. Decompose velocity into mean and fluctuating parts: U i (t) U i + u i (t). Similar fluctuations for pressure, temperature, and species concentration values Mechanics

14 Turbulence? Mechanics

15 Field work 2014 March: No fast ice 2015 March: Damping of waves in Tempelfjorden August: Galway bay oilslick 2016 March: Dicksonfjorden? April/May: Barentsea? May: Greenland? 2017 Templefjorden with MSc students Mechanics

16 Tempelfjorden, March 2015 Close to Longyearbyen Easy logistics Scope Test of new sensors for elevation of ice Can attenuation be detected? Change of wave speed along the fjord Velocities below the ice from the waves Mechanics

17 Project team, Svalbard 2015 Brian, Graig, Kai, Eugene, Erika, Atle, Trygve, Olav, Jean and Sebastian Mechanics

18 Mechanics

19 Tempelfjorden, sensor locations Mechanics

20 Topography 10 Distance N-S (km) Distance E-W (km) Mechanics

21 Raw signal Mechanics

22 Damping H S (m) V5 V2 V Time since T 0 (hr) Correlation coefficient ; Correlation waves V2-V7 Correlation envelope V2-V7 0.2 Correlation waves V5-V7 Correlation envelope V5-V Time since T 0 (hr) Mechanics

23 Svalbard March, 2016 Ice in Dicksonfjorden Measure velocities below ice Turbulent BL? Thickness and rheology Radar; ice and waves Autonome sensors for elevation Mechanics

24 Field Work - Svalbard - Grease Ice Mechanics

25 Grease II Mechanics

26 Grease III Mechanics

27 Field Work - Svalbard - Grease Ice F1 closest to shore, F2 and F3 further Clear attenuation in high frequency portion Mechanics

28 Field Work - Svalbard - Grease Ice Follows theoretical viscous damping curve relative well Mechanics

29 Lab experiments - Wave propagation in grease ice: a new mechanism for effective longitudinal elasticity Mechanics

30 Spatial damping coefficient α as a function of incoming wave frequency f. Blue curves indicate the results obtained with the one layer model of Weber (1987) without accounting for the effect of the boundary layers on the wavetank side and bottom walls and green curves indicate the results obtained with Eqn. (28) of Christensen (2005). The shaded region denotes 1 standard deviation in the best fit parameters. Left: results with the data reported by Newyear & Martin (1997). Right: results with the data obtained by the authors Mechanics

31 Field work 2017 MSc students from Mek4600 experimental methods in fluid mechanics Use theory and experience from laboratory experiments to describe real phenomena in the field Safety in the Arctic Measure motion of icebergs and currents Ice motion due to waves Mechanics

32 Pre test of ADCP - Oslo Mechanics

33 Mechanics

34 Test site - Tempelfjorden Mechanics

35 Kayak as research vessel Mechanics

36 Drift Mechanics

37 Packing and cleaning up Mechanics

38 Summary Theory, simulations, lab and field work to understand physics Observations; simulations in the lab Generation of turbulence from cover in the lab Numerical simulations; ice/waves What about oil? Mechanics