School of Mechanical Engineering Theses and Dissertations
http://hdl.handle.net/1853/5991
Original work by students in the School of Mechanical EngineeringSat, 22 Oct 2016 05:44:27 GMT2016-10-22T05:44:27ZParallel wavelet-adaptive direct numerical simulation of multiphase flows with phase-change
http://hdl.handle.net/1853/55692
Parallel wavelet-adaptive direct numerical simulation of multiphase flows with phase-change
Forster, Christopher J.
High-powered and high-energy density electronics are becoming more common with advances in computing, electric vehicles, and modern defense systems. Applications like these require efficient, compact, and economical heat exchanger designs capable of extremely large heat fluxes. Phase-change cooling methods allow for these characteristics; however, the design and optimization of these devices is extremely challenging. Numerical simulations can assist in this effort by providing details of the flow that are inaccessible to experimental measurements. One such system of interest to this work is acoustically enhanced nucleate boiling, which is capable of dramatic increases in the Critical Heat Flux (CHF). The focus of the present work is the development of a numerical simulation capable of predicting the behavior of acoustically enhanced nucleate boiling up to the CHF. A general-purpose wavelet-adaptive Direct Numerical Simulation (DNS) that runs entirely on the Graphics Processing Unit (GPU) architecture has been developed in this work to allow accurate, error-controlled simulation of a wide range of applications with multiphase flow at all Mach numbers. This work focuses on the development of a high-order simulation framework that can adequately address the challenges posed by acoustically enhanced nucleate boiling processes. Nucleate boiling in the presence of acoustic fields suffers from a large disparity of important time scales, namely the acoustic time scale and the convective time scale near the incompressible limit. To address this issue, the compressible Navier-Stokes equations are solved using a preconditioned dual-time stepping method to allow for accurate simulation of the flow for all Mach numbers, everywhere in the domain. The governing equations are solved on a wavelet-adaptive grid that provides a direct measure of local error and is adapted at every time step to follow the evolution of the flow for a significant reduction in computational resources and expense. The use of the wavelet-adaptive grid and the dual-time stepping method together allows for rigorous error control in both space and time. All components of this simulation have been redesigned and optimized for efficient implementation on the GPU architecture to offset the overhead of grid adaptation and further reduce time-to-solution. The development of the high-performance, error-controlled computational framework and its verification and validation is presented.
Thu, 04 Aug 2016 00:00:00 GMThttp://hdl.handle.net/1853/556922016-08-04T00:00:00ZForster, Christopher J.High-powered and high-energy density electronics are becoming more common with advances in computing, electric vehicles, and modern defense systems. Applications like these require efficient, compact, and economical heat exchanger designs capable of extremely large heat fluxes. Phase-change cooling methods allow for these characteristics; however, the design and optimization of these devices is extremely challenging. Numerical simulations can assist in this effort by providing details of the flow that are inaccessible to experimental measurements. One such system of interest to this work is acoustically enhanced nucleate boiling, which is capable of dramatic increases in the Critical Heat Flux (CHF). The focus of the present work is the development of a numerical simulation capable of predicting the behavior of acoustically enhanced nucleate boiling up to the CHF. A general-purpose wavelet-adaptive Direct Numerical Simulation (DNS) that runs entirely on the Graphics Processing Unit (GPU) architecture has been developed in this work to allow accurate, error-controlled simulation of a wide range of applications with multiphase flow at all Mach numbers. This work focuses on the development of a high-order simulation framework that can adequately address the challenges posed by acoustically enhanced nucleate boiling processes. Nucleate boiling in the presence of acoustic fields suffers from a large disparity of important time scales, namely the acoustic time scale and the convective time scale near the incompressible limit. To address this issue, the compressible Navier-Stokes equations are solved using a preconditioned dual-time stepping method to allow for accurate simulation of the flow for all Mach numbers, everywhere in the domain. The governing equations are solved on a wavelet-adaptive grid that provides a direct measure of local error and is adapted at every time step to follow the evolution of the flow for a significant reduction in computational resources and expense. The use of the wavelet-adaptive grid and the dual-time stepping method together allows for rigorous error control in both space and time. All components of this simulation have been redesigned and optimized for efficient implementation on the GPU architecture to offset the overhead of grid adaptation and further reduce time-to-solution. The development of the high-performance, error-controlled computational framework and its verification and validation is presented.Impact of connecting different types of energy simulation models for data center cooling and waste heat re-utilization
http://hdl.handle.net/1853/55691
Impact of connecting different types of energy simulation models for data center cooling and waste heat re-utilization
Mok, SeungHo
Data centers are the facilities that house information technology (IT) equipment used for our daily digital activities. They are considered as one of the largest energy consumers and also the fastest growing industries in the world. Since data centers consume a significantly large amount of electricity, which results in a large amount of heat that must be dealt with, data center cooling has been a very important topic. Due to such a large-scale system that a data center may require, it is critical to start with meticulously investigating cooling strategies for the data center before it begins to be constructed. The main purpose of this study is to develop energy simulation models that can be used to estimate overall data center efficiency for the location of interest. This large-scale modeling can be accomplished by developing several component-level models, which may be built in different modeling tools and interact with each other. This thesis considers four cooling scenarios of a 400 kW data center, and they are as follows: (a) an air cooled data center with a rotary regenerative heat exchanger and DX cooling system, (b) a hybrid cooled data center with an air cooled chiller and DX cooling system, (c) a hybrid cooled data center utilizing warm water through a liquid-to-liquid heat exchanger and DX cooling system, (d) a hybrid cooled data center that uses rear door heat exchangers and a water cooled chiller. As significant streams of waste heat are created from most data centers, this study also considers currently available or developmental low-grade waste heat re-use techniques including domestic heating, water pre-heating, and direct power generation from thermoelectric generators. Each component used in these scenarios is separately modeled in several modeling tools, and the component-level models will eventually be linked to run annual energy simulation for selected climate.
Mon, 01 Aug 2016 00:00:00 GMThttp://hdl.handle.net/1853/556912016-08-01T00:00:00ZMok, SeungHoData centers are the facilities that house information technology (IT) equipment used for our daily digital activities. They are considered as one of the largest energy consumers and also the fastest growing industries in the world. Since data centers consume a significantly large amount of electricity, which results in a large amount of heat that must be dealt with, data center cooling has been a very important topic. Due to such a large-scale system that a data center may require, it is critical to start with meticulously investigating cooling strategies for the data center before it begins to be constructed. The main purpose of this study is to develop energy simulation models that can be used to estimate overall data center efficiency for the location of interest. This large-scale modeling can be accomplished by developing several component-level models, which may be built in different modeling tools and interact with each other. This thesis considers four cooling scenarios of a 400 kW data center, and they are as follows: (a) an air cooled data center with a rotary regenerative heat exchanger and DX cooling system, (b) a hybrid cooled data center with an air cooled chiller and DX cooling system, (c) a hybrid cooled data center utilizing warm water through a liquid-to-liquid heat exchanger and DX cooling system, (d) a hybrid cooled data center that uses rear door heat exchangers and a water cooled chiller. As significant streams of waste heat are created from most data centers, this study also considers currently available or developmental low-grade waste heat re-use techniques including domestic heating, water pre-heating, and direct power generation from thermoelectric generators. Each component used in these scenarios is separately modeled in several modeling tools, and the component-level models will eventually be linked to run annual energy simulation for selected climate.Assignment and pursuit in temporally heterogeneous robotic teams
http://hdl.handle.net/1853/55677
Assignment and pursuit in temporally heterogeneous robotic teams
Oei, Marius Florian Bruno
Traditionally, robotic systems are built to move as fast as possible. In contrast to this, we investigate slowness and its effects on heterogeneous robotic teams inspired by biological systems. An assignment problem for static targets and a team pursuit problem for heterogeneous evaders are addressed.
The value of slowness in solving these problems optimally is examined. We further assemble the optimal teams for given problems by finding a compromise between performance and energy consumption or monetary cost. The results are validated in simulation and implemented on a robotic testbed.
Mon, 01 Aug 2016 00:00:00 GMThttp://hdl.handle.net/1853/556772016-08-01T00:00:00ZOei, Marius Florian BrunoTraditionally, robotic systems are built to move as fast as possible. In contrast to this, we investigate slowness and its effects on heterogeneous robotic teams inspired by biological systems. An assignment problem for static targets and a team pursuit problem for heterogeneous evaders are addressed.
The value of slowness in solving these problems optimally is examined. We further assemble the optimal teams for given problems by finding a compromise between performance and energy consumption or monetary cost. The results are validated in simulation and implemented on a robotic testbed.Shock and vibration isolation concepts through use of dynamic, multi-degree-of-freedom mechanical systems
http://hdl.handle.net/1853/55675
Shock and vibration isolation concepts through use of dynamic, multi-degree-of-freedom mechanical systems
Smith, Eric Christopher
Shock and vibration isolation continues to be an area of great interest to structural designers and to mount manufacturers. When the input disturbance is single-frequency or narrow-band, several techniques are available to limit vibration; e.g., vibration absorbers, use of active or passive damping or structural redesign. However, when the input disturbance is transient in nature or broadband, these isolation strategies are of limited effectiveness. Isolation systems are often modeled as single-degree-of-freedom systems, from which a qualitative picture of the design principles and tradeoffs can be viewed. The design space of isolation systems can be greatly expanded if one considers “dynamic” isolation systems. Passive, dynamic mounts can be thought of as multi-degree-of-freedom collections of springs, masses, and dampers. Such systems can be thought of as “mechanical filters” that attenuate and modify the shock disturbances before the disturbance reaches the isolation component. This dissertation explores several different multi-degree-of-freedom concepts for shock and vibration isolation; some of the systems are purely translational, others contain translational and rotational motion, some are linear while others exhibit varying degrees of nonlinearity. It is shown through numerical simulations, analytical approximations, and experimentation that the multi-degree-of-freedom mount designs can be very effective in accomplishing simultaneous shock and vibration isolation objectives with relatively simple, practical designs.
Wed, 27 Jul 2016 00:00:00 GMThttp://hdl.handle.net/1853/556752016-07-27T00:00:00ZSmith, Eric ChristopherShock and vibration isolation continues to be an area of great interest to structural designers and to mount manufacturers. When the input disturbance is single-frequency or narrow-band, several techniques are available to limit vibration; e.g., vibration absorbers, use of active or passive damping or structural redesign. However, when the input disturbance is transient in nature or broadband, these isolation strategies are of limited effectiveness. Isolation systems are often modeled as single-degree-of-freedom systems, from which a qualitative picture of the design principles and tradeoffs can be viewed. The design space of isolation systems can be greatly expanded if one considers “dynamic” isolation systems. Passive, dynamic mounts can be thought of as multi-degree-of-freedom collections of springs, masses, and dampers. Such systems can be thought of as “mechanical filters” that attenuate and modify the shock disturbances before the disturbance reaches the isolation component. This dissertation explores several different multi-degree-of-freedom concepts for shock and vibration isolation; some of the systems are purely translational, others contain translational and rotational motion, some are linear while others exhibit varying degrees of nonlinearity. It is shown through numerical simulations, analytical approximations, and experimentation that the multi-degree-of-freedom mount designs can be very effective in accomplishing simultaneous shock and vibration isolation objectives with relatively simple, practical designs.