Scaling Flat-Plate, Low-Temperature Adiabatic Effectiveness Results Using the Advective Capacity Ratio

Design of film-cooled engine components requires the ability to predict behavior at engine conditions through low-temperature testing. The adiabatic effectiveness, η, is one indicator film cooling performance. An experiment to measure η in a low-temperature experiment requires appropriate selection of the coolant flowrate. The mass flux ratio, M, is usually used in lieu of the velocity ratio to account for the fact that the coolant density is larger than that of the hot freestream at engine conditions. Numerous studies have evaluated the ability of M to scale η with mixed results. The momentum flux ratio, I, is an alternative also found to have mixed success, leading some to recommend matching the density ratio to allow simultaneous matching of M and I. Nevertheless, inconsistent results in the literature regarding the efficacy of these coolant flowrate parameters to scale the density ratio suggest other properties also play a role. Experiments were performed to measure η on a flat plate with a 7-7-7-shaped hole. Various coolant gases were used to give a large range of property variations. We show that a relatively new coolant flowrate parameter that accounts for density and specific heat, the advective capacity ratio, far exceeds the ability of either M or I to provide matched η between the various coolant gases that exhibit extreme property differences. With the specific heat of coolant in an engine significantly lower than that of the freestream, advective capacity ratio (ACR) is appropriate for scaling η with non-separating coolant flow.

Sustainable Evolution in an Ever-Changing Environment

It is suggested that the notion of equation-of-state serves as appropriate common basis for studying the macroscopic behavior of both traditional physical systems and complex systems. The reason is that while the equilibrium systems are characterized both by their energy function and the corresponding equation-of-state, the steady states of out-of-equilibrium systems are defined only by their dynamics, i.e. by their equations-of-state. It is demonstrated that there exists a common measure which generalizes the notion of Gibbs measure so that it acquires two-fold meaning: it appears both as local thermodynamical potential and as probability for robustness to environmental fluctuations. It is proven that the obtained Gibbs measure has very different meaning and role than its traditional counterpart. The first one is that it is derived without prerequisite requirement for simultaneous achieving of any extreme property of the system such as maximization of the entropy.

BLACK HOLES HAVE A GOOD TEMPER(ATURE)

It is well known that black holes are the most extreme objects in nature: they have the maximal energy and entropy capacities allowed by the laws of physics. In this essay we reveal another extreme property of these fascinating objects: black holes have the fastest relaxation dynamics allowed by a quantum theory of gravity. From information theory and thermodynamic considerations a universal bound on the relaxation time τ of a perturbed physical system is inferred, τ ≥ ħ/πT, where T is the system's temperature. We then show that black holes may actually attain this fundamental bound, which makes them the fastest-relaxing objects in the universe.

Mohr-Coulomb Failure Condition and the Direct Shear Test Revisited

An alternative critical plane orientation is proposed in the Mohr-Coulomb failure criterion for soils with an extreme property. Parameter identification from the direct shear test is extended to incude the lateral normal stress.