We embedded a linear programming timber harvest scheduling model into an aspatial stochastic simulation model of a flammable forest to evaluate two fire risk mitigation strategies. The harvest scheduling model is solved repeatedly to produce harvest schedules within a rolling planning horizon framework. The risk mitigation strategies we examined were (1) whether or not to account for fire in the planning model and (2) replanning interval. We evaluated those strategies under four representative fire regimes. We found that accounting for fire in the planning model reduced the harvest volume variability as fire activity increased (i.e., for average annual burn fractions ≥0.45%), but replanning intervals over a range of 1 to 10 years had little impact on harvest volume variability. We also developed a risk analysis decision-making aid that forest managers can use to help deal with fire-related uncertainty. Our results suggest that risk-averse forest managers should account for fire while planning, especially when burn fractions exceed 0.45%.

Heat transfer from rough surfaces to flowing fluids is of interest because of the high heat transfer rates that can be obtained in equipment of small volume. The increase in heat transfer rate is generally owing to both an increase in the area of the surface and an increase in the heat transfer Coefficient. The increase in heat transfer coefficient is owing to a change in the turbulence pattern close to the wall brought about by the presence of the surface protuberances. Unfortunately, the increase in heat transfer rate brought about by roughening a surface is usualIy accompanied by a large increase in the energy needed to move the fluid across the surface; as a consequence the heat transfer per unit of power consumption is often less for a rough surface than for a smooth surface. It is therefore of economic, as well as academic, interest to determine what type or types of roughness will produce the maximum rate of heat transfer per unit of power consumption.The approach adopted in this study was to consider a simple type of roughened surface, transverse fins on the inside wall of a circular pipe, and focus attention on one single test fin. Arrays of identical fins were placed upstream and downstream from the test fin to establish a developed velocity field at the test fin and to provide a roughened length over which overall pressure-drop measurements could be taken. The actual experimental system employed had a test fin, at which heat transfer and form drag measurements were made, that was integral with the pipe wall. The arrays of fins on either side of the test fin were a sliding fit in the circular pipe making it relatively easy to vary the spacing between consecutive fins.The main objectives of the research were to measure the contribution of form drag to the total forces retarding flow for different roughness configurations and Reynolds numbers, and to measure the average heat transfer coefficient around a typical singIe protuberance as well as the effect of fin height and fin spacing on this average coefficient. The effect of Prandtl number was also studied. THEORY AND PREVIOUS WORKPast work can be classified in terms of the flow regime in which the studies were made. The term "transition regime" refers to flow and roughness conditions for which the overall friction coefficient depends on both the roughness and the Reynolds number. The term "fully rough regime" describes conditions where the overall friction coefficient is independent of Reynolds number and depends only on the roughness.The effect of wall roughness in conduits on heat and momentum transfer has been studied by many workers.Early friction studies were made by Nikuradse ( 1 ) and Schlichting ( 2 ) ; heat and momentum transfer studies in the transition flow regime have been made by Stanton ( 3 ) , Kemeny and Cyphers ( 4 ) , Smith and Epstein ( 5 ) , and Hastrup et al. ( 6 ) . For the fully rough flow region, which is the flow condition which prevailed in the experiments described here, the literature contains reports of investigations by Cope...

Ecological values are an important aspect of sustainable forest management, but little attention has been paid to maintaining these values when using traditional linear programming (LP) forest management planning models in uncertain planning environments. We embedded an LP planning model that specifies when and how much to harvest in a simulation model of a “managed” flammable forest landscape. The simulation model was used to evaluate two strategies for dealing with fire-related uncertainty when managing mature and old forest areas. The two seral stage areas were constrained in the LP planning model to a minimum of 10% of the total forest area and the strategies were evaluated under four representative fire regimes. We also developed a risk analysis tool that can be used by forest managers that wish to incorporate fire-related uncertainty in their decision-making. We found that use of the LP model would reduce the areas of the mature and old forest to their lower bound and fire would further reduce the seral areas below those levels, particularly when the mean annual burn fraction exceeds 0.45% per annum. Increasing the minimum area required (i.e., the right-hand side of the constraint) would increase the likelihood of satisfying the minimum area requirements.