Numerical Calculation of Fracture Seepage in Rough Rock and Analysis of Local Pressure Drop

The seepage performance of a rock mass mainly depends on the rock fractures developed in it. Numerical calculation method is a common method to study the permeability properties of fractures. Seepage in rock fractures is affected by various factors such as fracture aperture, roughness, and filling, among which aperture and roughness are the two most widely influenced factors. The Navier-Stokes (NS) equation can be solved directly for the seepage flow in rock fractures with good accuracy, but there are problems of large computational volume and slow solution speed. In this paper, the fracture aperture space data is substituted into the local cubic law as an aperture function to form a numerical calculation method for seepage in rough rock fractures, namely, the aperture function method (AFM). Comparing with the physical seepage experiments of rock fractures, the calculation results of AFM will produce a small amount of error under the low Reynolds number condition, but it can greatly improve the calculation efficiency. The high efficiency of calculation makes it possible to apply AFM to the calculation of large-scale 3D rough fracture network models. The pressure drop of fluid in the fracture has viscous pressure drop (VPD) and local pressure drop (LPD). VPD can be calculated using the AFM. After analyzing the results of solving the NS equation for fracture seepage, it is concluded that the LPD includes the pressure drop caused by area crowding in the recirculation zone (RZ), kinetic energy loss in the RZ, kinetic energy loss in the vortices, and other reasons.

Cosmic Gas Thermodynamics at z = 1089

The Universe at z = 1089 is treated as an expanding ideal gas. Its internal kinetic energy loss exceeds the amount absorbed by gravity and drives further expansion. A Hubble relation (Hg) is derived and compared to the value found by the ΛCDM model (HΛ) over the range z = 1089 to 0. The results suggest that the adiabatic release of energy from cosmic gas accounts for about half of present-day Universal expansion.

Определение расходных характеристик сопловых аппаратов с сверхзвуковыми прямоугольными соплами при моделировании переменных режимов малорасходных турбин

В работе приводятся обобщающие зависимости коэффициентов расхода сопловых аппаратов с сверхзвуковыми прямоугольными соплами в широком диапазоне изменения определяющих геометрических и режимных параметров, базирующиеся на экспериментальном материале по коэффициентам расхода для транс- и дозвуковых решеток профилей. Получены эмпирические формулы, учитывающие влияние степени конфузорности, относительной высоты сопел и числа Рейнольдса на коэффициент расхода соплового аппарата. Показано слабое влияние на коэффициент расхода относительного шага сопел в области его оптимальных значений определенных по минимуму потерь кинетической энергии и числа Маха. Переменные режимы работы сопла учитываются зависимостью относительного коэффициента расхода в функции от числа Рейнольдса. Полученные в работе эмпирические зависимости позволяют использовать их при моделировании переменных режимов и многорежимной оптимизации малорасходных турбин.The research introduces generalizing functions of mass flow rates in supersonic rectangular nozzle diaphragms in wide variation range of controlling geometry and duty parameters, based on experimental material on the mass flow rates for trans- and subsonic cascades. Empirical functions which take into account influence of convergence ratio, the relative height of the nozzles and the Reynolds number on the mass flow rate of nozzle diaphragms are obtained. It is shown that the relative nozzle step in the area of its optimal values determined from the minimum kinetic energy loss and Mach number slightly effects on the mass flow rate. Variable duties of the nozzle are taken into account by the dependence of the relative mass flow rate from the Reynolds number. The empirical dependences obtained in the paper allow using them in modeling variable duties and multimode optimization of low-consumption turbines.

Nuclear structure in the neutron-deficient Sn nuclei TKEL effects on lifetime measurements

The presence of seniority-like isomers along the Z = 50 isotopic chain have been an experimental limitation to the investigation of the electromagnetic properties of the low-lying states in the light Sn nuclei. Combining a multi-nucleon transfer reaction with the Recoil-Distance Doppler-Shift technique, the lifetimes of the 21+ and 41+ excited states have been directly measured in the neutron-deficient 106, 108Sn isotopes for the very first time. The emitted γ rays were detected by the AGATA array, while the reactionproducts were uniquely identified by the VAMOS++ magnetic spectrometer. The control of the direct feeding of the statesby gating on the Total Kinetic Energy Loss, together with the unique capabilities of the two spectrometers, was crucial for the measurementin 108Sn.

Numerical modelling of transonic centripetal flow in radial turbine blade cascade

Numerical modelling of transonic centripetal turbulent flow in radial blade cascade is described in this paper. Method of the confusor buffer zone is applied to overcome some numerical obstacles related with specifical properties of the outlet confusor. Kinetic energy loss coeficient of the radial blade cascade is compared with its linear representation and with experimental data.

Aerodynamic Data for Two Variants of Root Turbine Blade Sections for a 54″ Turbine Rotor Blade

Aerodynamic investigations were performed on planar blade cascades representing two alternative root sections of rotor blades 54″ in length with straight fir-tree root. Each of the variants was designed for different number of blades in the rotor. This paper presents the results of measurements showing the dependency of the kinetic energy loss coefficient and the exit flow angle on the exit isoentropic Mach number and the angle of incidence. Images of the flow fields are also presented. The experimental data is analyzed to assess and document the difference between the two root section designs. Results show that requirement of straight fir tree root leading to high design incidence angles significantly limit operation range. Also in case of root sections with high exit Mach numbers a limit load conditions are an issue. In order to utilize available pressure drop blade cascade throat/pitch ratios should be kept as high as possible which favorites variant with lower number of blades and higher outlet metal angle (relative to axial direction).

Experimental Observations of Flow Over an Airfoil in a Confined Duct

The flow around a NACA 0020 airfoil strut placed in the centre of a rectangular duct has been studied. The performance of the strut was characterized in terms of its effect on the mean flow, as well as in terms of overall losses. It was shown that the main influences of increasing the confined mixing length downstream of the airfoil wake were to reduce the total system dump loss (kinetic energy loss) through the use of a Carnot diffuser, and to slightly increase the wake spreading rate. In addition to creating a reference dataset for CFD comparison and validation, some phenomenon were particularly identified for future CFD investigation. It was shown that there may be some benefit to adjusting the turbulent Prandtl number for Turbulent Kinetic Energy during CFD simulations of this same problem. It was also shown that studying the particular effects of the Carnot diffuser on the development and migration of the wall-airfoil interface vortices would give useful insight into the physical mechanisms driving this change in performance.