Glen H. Wheless

A review of tele-immersive applications in the CAVE research network

This paper presents an overview of the tele-immersion applications that have been built by collaborators around the world using the CAVERNsoft toolkit, and the lessons learned from building these applications. In particular the lessons learned are presented as a set of rules-of-thumb for developing tele-immersive applications in general.

Virtual Chesapeake Bay: interacting with a coupled physical/biological model

The Chesapeake Bay Virtual Environment (CBVE) is a multidisciplinary, collaborative project that fuses 3D visualizations of numerically generated output, observations and other data products into a large-scale, interactive virtual world that supports investigation of coupled physical/biological and environmental processes. Although still under development, CBVE provides an application framework for integrating circulation and biological models with the computer visualization paradigm of the virtual world. In this article, we first briefly describe the physical environment and the observed effects of winds, tides and river runoff on the Chesapeake Bay system. Then we describe the CBVE components and conclude with our efforts directed at understanding how environmental variability may affect the recruitment and retention of the larval phase of certain local marine species.

Inflows/outflows at the transition between a coastal plain estuary and the coastal ocean

Abstract A series of numerical experiments were performed to study the dynamics at the transition region between a wide (Kelvin number between 2 and 3.6) coastal plain estuary and the adjacent coastal ocean. In particular, the separate effects of modifying the seaward discharge within the estuary, the coastal ambient flow, the coastal ocean bottom slope, and the initial salinity gradient were investigated. The numerical experiments were carried out in a flat-bottom estuary with a N-S orientation that is connected to the ocean in the E-W direction. Results show that increased seaward discharge at the estuary upstream boundary reduces volume inflow and increases volume outflow through a cross-section at the estuary mouth. A southward coastal ambient flow is responsible for increased volume inflow, for keeping estuarine outflow within a few kilometers from the coast, for increasing surface flow divergence at the estuary mouth, and for hindering inflow that originates to the south of the estuary. When the coastal ambient flow is suppressed, the bottom slope of the coastal ocean causes negligible effects to volume transports, to the dynamcal balances, and to the shape and extent of inflows/outflows compared to results over a flat bottom. These effects of the bottom slope become non-negligible but are still minor when the coastal ambient flow is active. A pulse of buoyant water at the estuary upstream boundary causes, after the discharge stops, increased volume inflow with respect to other experiments. Increased salinity gradients produce enlargements to the deformation radii, the volumes exchanged, and the regions directly influenced by inflows and outflows.

A modeling study of tidally driven estuarine exchange through a narrow inlet onto a sloping shelf

The circulation and particle transport through a narrow inlet (Kelvin number < 0.5) and onto a sloping shelf are numerically examined using a three-dimensional hydrodynamic model. The model domain consists of an estuarine basin with vertical density stratification separated from a well-mixed sloping shelf by a narrow inlet. Forcing is supplied by semidiurnal tides and buoyancy differential. Strong ebb flows resulting from this combined forcing transport estuarine water seaward through the inlet to form a radially spreading buoyant surface plume over the shelf. A series of radial density fronts corresponding with the ebbing tidal outflow are found on the seaward side of the inlet mouth and are convergence zones for floating particles. Strong anticyclonic frontal flow advects particles around the boundary of the outflow plume. Particles released nearest the seaward side of the inlet mouth are able to enter the inlet at depth and remain, while those particles released farther offshore rarely enter the inlet. This result has clear implications for the shelf-to-estuary transport of pollutants or the larval phase of marine species. Asymmetric tidally induced eddies which appear on both sides of the inlet also contribute to the near-field circulation. Calculations of gradient Richardson number in the inlet show that regions susceptible to enhanced mixing occur during periods of maximum tidal velocities due to increased shear.

Enhanced stratification in the lower Chesapeake Bay following northeasterly winds

Abstract Density data from a lower Chesapeake Bay transect obtained after two northeasterly wind events were used to describe the effects of these events on the density field in the lower estuary. The first northeaster occurred in early August 1995 and the second northeaster was related to the passage of hurricane Felix off the lower bay in mid-August 1995. The latter northeaster prolonged a period of persistent winds from the N and NE that began in early August and caused storm surges of similar magnitude to the former northeaster. The salinity fields observed after the early August event suggested encroachment of coastal waters into the lower bay as reflected by high salinities throughout the transect. Two days after weakening of the winds related to Felix, the density distribution across the lower bay showed strongly stratified conditions. This behavior suggested that the inflow of coastal water into the lower bay and the wind mixing related to Felix combined to produce a vertically uniform density gradient perpendicular to the bay entrance that relaxed after the winds weakened. This weakening of the winds coincided with neap tidal currents, which were not energetic enough to maintain vertical homogeneity and must have allowed the self-adjustment of the density gradient and the seaward advection of relatively buoyant waters near the surface. These mechanisms were illustrated with simplified numerical experiments. The findings of this study are used to propose the hypothesis that, in general, enhanced stratification and flushing in the lower bay will ensue the relaxation of a northeasterly wind event, provided that this relaxation coincides with a weak friction regime, i.e., neap tides.

Use of collaborative virtual environments in the mine countermeasures mission

We describe our work on the development and use of collaborative virtual environments to support planing, rehearsal, and execution of tactical operations conducted as part of mine countermeasures missions (MCM). Utilizing our VR-based visual analysis tool, Cave5D, we construct interactive virtual environments based on graphical representations of bathymetry/topography, above-surface imags, in-water objects, and environmental conditions. The data sources may include archived data stores and real-time inputs from model simulations or advanced observational platforms. The Cave5D application allows users to view, navigate, and interact with time-varying data in a fully 3D context, thus preserving necessary geospatial relationships crucial for intuitive analysis. Collaborative capabilities have been integrated into Cave5D to enable users at many distributed sites to interact in near real-time with each other and with the data in a many-to-many session. The ability to rapidly configure scenario-based missions in a shared virtual environment has the potential to change the way mission critical information is used by the MCM community.

Data visualization and analysis from within a collaborative virtual environment: applications for littoral warfare

We describe our continuing work on the development and use of collaborative virtual environments (CVEs) in support of Naval Special Warfare mission rehearsal activities for the very shallow water mine countermeasures mission. These multi-participant CVEs are built form multiple data streams that include archived numerical circulation model results, 3D model files, moving entities and observations from advanced instrumentation and autonomous underwater vehicles. A room-sized multi-walled projection device known as a CAVE is used to provide an immersive quality to the simulations thereby adding to the realism of data presentation activities. Asynchronous collaborative capability allows users at many remote sites to partake in a many-to-many session that takes place in a common virtual world. A participant is able to view, navigate through and interact with the data and with other users in the 3D environment. Typical data types represented in the mine countermeasures CVE include graphical representations of bathymetry/topography, above-surface images, in-water objects, high-resolution data and hydrographic characteristics.

Mission rehearsal using collaborative virtual environments

We describe our continuing work on the development and use of collaborative virtual environments (CVEs) in support of mission rehearsal activities for the very shallow water mine countermeasures mission. These multi-participant CVEs are built from multiple data streams that include archived circulation model results, 3D model files, moving entities and observations from advanced instrumentation. A room-sized projection screen device called the CAVETM is used to visualize and interact with the CVE, although single walled devices and workstations may also be used. Asynchronous collaborative capability allows users at many distributed sites to partake in a many-to-many session that takes place in a common virtual world. Incorporating multiple data streams, these CVEs allow multiple users to view, navigate, and interact with data in a 3D environment, including graphical representation of bathymetry/topography, above- surface images, in-water objects (e.g. mines, bridges), and hydrographic characteristics (e.g. currents, water levels, temperature).