Inverse solution of surface mass balance of Midtre Lovénbreen, Svalbard

ABSTRACTWe investigate the temporal evolution and spatial distribution of mass balance on the glacier Midtre Lovénbreen, Svalbard. Running a diagnostic high-resolution full-stress ice flow model with geometries obtained from five digital elevation models (DEMs) in the period 1962–2005, we compute velocity fields and linearly interpolated volume change of the glacier. We evaluate the kinematic free surface equation using these model outputs to solve the surface mass balance (SMB). Monitoring data on Midtre Lovénbreen allows model results to be compared with point measurements from the glacier over several decades. This method allows us to estimate the mass balance over the entire glacier surface, beyond the spatially limited field measurements, and to derive past SMB over an extended time period.

Modeling of Two-Stage Solidification: Part I Model Development

The paper presents a new numerical model of solidification processes in hypoeutectic alloys. The model combines stochastic elements, such as e.g. random nucleation sites and orientation of dendritic grains, as well as deterministic methods e.g. to compute velocity of dendritic tips and eutectic grains. The model can be used to determine the temperature and the size of structure constituents (of both, the primary solid phase and eutectics) and the arrangement of individual dendritic and eutectic grains in the consecutive stages of solidification. Two eutectic transformation modes, typical to modified and unmodified hypoeutectic alloys, have been included in the model. To achieve this, cellular automata and Voronoi diagrams have been utilized.

Calculation of the Die Entry Flow of a Concentrated Polymer Solution Using Micro-Macro Simulations

A micro-macro simulation algorithm for the calculation of polymeric flow is developed and implemented. The algorithm couples standard finite element techniques to compute velocity and pressure fields with stochastic simulation techniques to compute polymer stress from simulated polymer dynamics. The polymer stress is computed using a microscopic-based rheological model that combines aspects of network and reptation theory with aspects of continuum mechanics. The model dynamics include two Gaussian stochastic processes, each of which is destroyed and regenerated according to a survival time randomly generated from the material’s relaxation spectrum. The Eulerian form of the evolution equations for the polymer configurations is spatially discretized using the discontinuous Galerkin method. The algorithm is tested on benchmark contraction domains for a polyisobutylene solution. In particular, the flow in the abrupt die entry domain is simulated and the simulation results are compared to experimental data. The results exhibit the correct qualitative behavior of the polymer and agree well with the experimental data.

EVALUATION OF TURBULENCE PARAMETERS IN LABORATORY FLASKS USED FOR DISPERSANT EFFECTIVENESS TESTING

ABSTRACT The effectiveness of dispersants used as countermeasures for oil spills is commonly evaluated by conducting tests in laboratory flasks. The success of the test relies on the replication of sea conditions in the flasks. We used a Hot-wire Anemometer (HWA) to characterize the hydraulics in the Swirling Flask (SF) and the Baffled Flask (BF) at orbital shaker speeds of 150 and 200 rpm's. We used these measurements to compute velocity gradient, G, turbulence microscale, η, and energy dissipation rate per unit mass, ɛ. The flask average energy dissipation rates in the SF were about two orders of magnitude smaller than those in the BF. The sizes of the microscales in the SF were found to be much smaller than that in the SF. Also, in the BF, the sizes of the microscales approached the size of oil droplets observed at sea (50 to 400 micron), which means that the hydraulics in the BF closely resembles the hydraulics occurring in the top few cm of a breaking wave. Hence, the BF is preferable for dispersant effectiveness testing in the laboratory.

Calculation of Polymer Flow Using Micro-Macro Simulations

A micro-macro simulation algorithm for the calculation of polymeric flow is developed and implemented. The algorithm couples standard finite element techniques to compute velocity and pressure fields with stochastic simulation techniques to compute polymer stress from simulated polymer dynamics. The polymer stress is computed using a microscopic-based rheological model which combines aspects of network and reptation theory with aspects of continuum mechanics. The model dynamics include two Gaussian stochastic processes each of which is destroyed and regenerated according to a survival time randomly generated from the material’s relaxation spectrum. The Eulerian form of the evolution equations for the polymer configurations are spatially discretized using the discontinuous Galerkin method. The algorithm is tested on benchmark contraction domains for a polyisobutylene (PIB) solution. In particular, the flow in the abrupt die entry domain is simulated and the simulation results are compared with experimental data. The results exhibit the correct qualitative behavior of the polymer and agree well with the experimental data.