Bulletin of the American Physical Society
72nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 64, Number 13
Saturday–Tuesday, November 23–26, 2019; Seattle, Washington
Session P03: Fluid Mechanics General |
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Room: 201 |
Monday, November 25, 2019 5:16PM - 5:29PM |
P03.00001: Zermelo’s problem: Optimal point-to-point navigation in 2D turbulent flows using Reinforcement Learning Michele Buzzicotti, Luca Biferale, Fabio Bonaccorso, Patricio Clark Di Leoni, Kristian Gustavsson To find the path that minimizes the time to navigate between two given points in a fluid flow is known as the Zermelo's problem. Here, we investigate it by using a Reinforcement Learning (RL) approach for the case of a vessel which has a slip velocity with fixed intensity, $V_{\rm s}$, but variable direction and navigating in a 2D turbulent sea. We use an Actor-Critic RL algorithm, and compare the results with strategies obtained analytically from continuous Optimal Navigation (ON) protocols. We show that for our application, ON solutions are unstable for the typical duration of the navigation process, and are therefore not useful in practice. On the other hand, RL solutions are much more robust with respect to small changes in the initial conditions and to external noise, and are able to find optimal trajectories even when $V_{\rm s}$ is much smaller than the maximum flow velocity. Furthermore, we show how the RL approach is able to take advantage of the flow properties in order to reach the target, especially when the steering speed is small. [Preview Abstract] |
Monday, November 25, 2019 5:29PM - 5:42PM |
P03.00002: Thermo-mechanics modeling and physics David Kassoy, Adam Norris Thermal energy deposition into a finite volume of gas is the immediate source of thermodynamic and velocity disturbances. The thermo-mechanical response in a given geometry and system depends on a variety of physical parameters including the time scale and quantity of heat deposition into the volume, and on the time scale that characterizes acoustic disturbances in the volume. Thermo-mechanical modelling is based on the \textbf{non-dimensional} reactive Navier-Stokes equations. The relevant \textbf{non-dimensional} parameters include: $\backslash $parda. ; the ratio of the characteristic time scale for heat release to the acoustic time scale of the volume, \textbf{. q}$_{\mathrm{\mathbf{R:}}}$\textbf{:}$_{\mathrm{\mathbf{\thinspace }}}$\textbf{the ratio of the characteristic heat of reaction to the initial internal energy level in the volume, . : the traditionally defined high activation parameter.}$\backslash $\textbf{pardNumerical results, based on the reactive Euler equations, are described for a wide range of non-dimensional} parameters defined above. They are compared with asymptotic analytical results, obtained for a variety of limiting parameter values, that including non-intuitive nearly constant volume, nearly isobaric and fully compressible responses to energy deposition. [Preview Abstract] |
Monday, November 25, 2019 5:42PM - 5:55PM |
P03.00003: Great operation Han Yongquan The even general formula is: 2n, where n is an integer greater than 1, and 2n can decompose the prime factor, that is, 2n$=$N1N2N3..., where N1, N2, N3, ... are all prime numbers. 2n, N1N2N3... must be written as the sum of two identical odd numbers or the sum of two identical even numbers, whichever comes first. That is, it can be learned: 2n$=$(m$+$m), m$=$N1N2N3.../2, when m is a prime number (specially pointed out: when n$=$2, 2n$=$2$+$2), the proposition is proved. When m is a composite number, it is proved as follows: When m is an even number, m adds an odd number or subtracts an odd number to exhaust all odd numbers, and since more than 2 prime numbers must exist in the odd number, it is sure to find the sum of the two prime numbers to represent any even number (2n). When m is an odd number, m plus an even number or an even number can also exhaust all odd numbers, and since more than 2 prime numbers must exist in odd numbers, the sum of two prime numbers must be found to represent any even number (2n). . That is, 2n$=$[(N1N2N3.../2-a)$+$(N1N2N3.../2$+$a)] ...1, whether a is an odd number when m is an even number, or a is an odd number when m is an odd number, 1 It can always be established.the Goldbach conjecture can be proved. [Preview Abstract] |
Monday, November 25, 2019 5:55PM - 6:08PM |
P03.00004: Reserves Classification and Well Pattern Infilling Adjustment in Tight Sandstone Gas Field Zhi Guo, Ailin Jia Sulige is typical of tight sandstone gas field in China, with poor reservoir property and strong heterogeneity. The recovery factor is only about 30{\%} under the current developing well pattern of 600m×800m. Thus it is necessary to evaluate various types of reserves comprehensively and implement well pattern infilling adjustment respectively. Through fine reservoir description in dense well pattern and interference well test analysis, the reservoir distribution frequency was studied and reserves were classified into five types. Compared actual production data with modeling {\&} simulation result, the relation of well pattern density, interference degree and recovery factor was researched for each type of reserves. Then, it can be concluded the appropriate well pattern density in various type of reserves area is 2\textasciitilde 4 wells per square kilometers, and the ultimate recovery factor is about 50{\%}. This research, makes reserves configuration clear in the tight sandstone gas field, provides geological basis for well pattern infilling adjustment in later development stage, lays a solid foundation for long-term stable production of gas field, and is also of certain reference significance to other gas field development under similar geological conditions. [Preview Abstract] |
Monday, November 25, 2019 6:08PM - 6:21PM |
P03.00005: Technologies advancement and prospect of natural gas development in China Ailin Jia, Zhi Guo In recent years, international oil prices have stayed low and China strives to develop green energy. Under these backgrounds, natural gas has gradually become the key business of petroleum industry in China. After years of hardworking, several developmental technological breakthroughs are achieved for deep gas, tight gas, shale gas, coal-bed methane, development adjustment strategies, engineering technologies and decision-making system. With the depth of development, influenced by policy, environment and geological conditions, continuous efficient development of domestic natural gas faces many challenges: lower ratio of good quality reserves, more development expense, larger difficulties of remaining development benefit for unconventional gas reservoir, further upstream benefit compression, poorer stable production ability and fiercer competition in the energy market. In the future, natural gas development in China will enter into a new stage of emphasizing on both the unconventional gas and the conventional gas, gas imports will rise year by year, resulting in the increased external dependency, and natural gas will become the main growth engine in the process of energy structure adjustment. [Preview Abstract] |
Monday, November 25, 2019 6:21PM - 6:34PM |
P03.00006: Plume-Chimney in Natural Convection from Large Sources. Christopher Chu A natural draft chimney is defined by the existence of buoyancy and a solid wall barrier between two regions of fluids that differ in density. By preventing the mixing of two fluids at different densities in a fluid environment, there is effectively a wall-like characteristic, a chimney system without the solid walls. An ``effective plume height'' was pioneered by heat transfer engineers to close the solution loop of the natural convection performance of forced draft air-cooled heat exchangers, by modifying an atmospheric plume rise model. An improved prediction method was later developed and satisfactorily validated by both experiments and computational fluid dynamics (CFD) simulation of the natural convection performance of an industrial-scale air-cooled heat exchanger. The flow development region that has been identified in the field of jets is known as the zone of flow establishment (ZFE), but in lazy plumes of low Froude number it has stack effect. Two reasons for justifying the concept of plume-chimney are: 1) it affects the draft of a natural convection system of large source area by extending the solid-walled chimney height and 2) its existence anticipates a potential blockage to cross current such as wind in real natural convection systems, modifying the flow pattern. [Preview Abstract] |
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