Advanced search options

Advanced Search Options 🞨

Browse by author name (“Author name starts with…”).

Find ETDs with:

in
/  
in
/  
in
/  
in

Written in Published in Earliest date Latest date

Sorted by

Results per page:

Sorted by: relevance · author · university · dateNew search

You searched for subject:(Impact Angles). Showing records 1 – 3 of 3 total matches.

Search Limiters

Last 2 Years | English Only

No search limiters apply to these results.

▼ Search Limiters

1. Oliveira, Denny. A study of interplanetary shock geoeffectiveness controlled by impact angles using simulations and observations.

Degree: PhD, 2015, University of New Hampshire

In this dissertation, we study the influence of interplanetary (IP) shock impact angles in the IP shock geoeffectiveness focusing on simulations and observations. In our simulations, we use OpenGGCM global MHD code to study the nightside magnetospheric, magnetotail, and ionospheric responses to IP fast forward shocks. Three cases are presented in this study: two inclined oblique shocks, hereafter IOS-1 and IOS-2, where the latter has a Mach number twice stronger than the former. Both shocks have impact angles of 30o in relation to the Sun-Earth line. Lastly, we choose a frontal perpendicular shock, FPS, whose shock normal is along the Sun-Earth line, with the same Mach number as IOS-1. We find that, in the IOS-1 case, due to the north-south asymmetry, the magnetotail is deflected southward, leading to a mild compression. The geomagnetic activity observed in the nightside ionosphere is then weak. On the other hand, in the head-on case, the FPS compresses the magnetotail from both sides symmetrically. This compression triggers a substorm allowing a larger amount of stored energy in the magnetotail to be released to the nightside ionosphere, resulting in stronger geomagnetic activity. By comparing IOS-2 and FPS, we find that, despite the IOS-2 having a larger Mach number, the FPS leads to a larger geomagnetic response in the nightside ionosphere. As a result, we conclude that IP shocks with similar upstream conditions, such as magnetic field, speed, density, and Mach number, can have different geoeffectiveness, depending on their shock normal orientation. In the second part of this dissertation, we present a survey of fast forward IP shocks using WIND and ACE satellite data from January 1995 to December 2013 to study how IP shock geoeffectiveness is controlled by IP shock impact angles. A shock list covering one and a half solar cycle is compiled. The yearly number of IP shocks is found to correlate well with the monthly sunspot number. We use data from SuperMAG, a large chain with more than 300 geomagnetic stations, to study geoeffectiveness triggered by IP shocks. The SuperMAG SML and SME indices, enhanced versions of the familiar AL and AE indices, are used in our statistical analyses to quantify substorm strength and auroral power (AP) intensity, respectively. The jumps of the SML index and the calculated AP intensity triggered by IP shock impacts on the Earth's magnetosphere are investigated in terms of IP shock orientation and speed. We find that, in general, strong (high speed) and almost frontal (shock normal almost parallel to the Sun-Earth line) shocks are more geoeffective than inclined shocks with low speed. The highest correlations (correlation coefficient R = 0.78 for SML, and R = 0.79 for AP) occur for fixed IP shock speed and varying the IP shock impact angle. We attribute this result, predicted previously by simulations, to the fact that frontal shocks compress the magnetosphere symmetrically from all sides, which is a favorable condition for the release of magnetic energy stored in the… Advisors/Committee Members: Joachim Raeder, Charlie Farrugia, Martin Lee.

Subjects/Keywords: auroral power intensity; geomagnetic activity; impact angles; interplanetary shocks; substorm strength; Plasma physics; Physics

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Oliveira, D. (2015). A study of interplanetary shock geoeffectiveness controlled by impact angles using simulations and observations. (Doctoral Dissertation). University of New Hampshire. Retrieved from https://scholars.unh.edu/dissertation/2205

Chicago Manual of Style (16th Edition):

Oliveira, Denny. “A study of interplanetary shock geoeffectiveness controlled by impact angles using simulations and observations.” 2015. Doctoral Dissertation, University of New Hampshire. Accessed December 09, 2019. https://scholars.unh.edu/dissertation/2205.

MLA Handbook (7th Edition):

Oliveira, Denny. “A study of interplanetary shock geoeffectiveness controlled by impact angles using simulations and observations.” 2015. Web. 09 Dec 2019.

Vancouver:

Oliveira D. A study of interplanetary shock geoeffectiveness controlled by impact angles using simulations and observations. [Internet] [Doctoral dissertation]. University of New Hampshire; 2015. [cited 2019 Dec 09]. Available from: https://scholars.unh.edu/dissertation/2205.

Council of Science Editors:

Oliveira D. A study of interplanetary shock geoeffectiveness controlled by impact angles using simulations and observations. [Doctoral Dissertation]. University of New Hampshire; 2015. Available from: https://scholars.unh.edu/dissertation/2205

2. Zu, Marion Aku Atsine. A Numerical Investigation of the Slamming Event Through FSI Analysis .

Degree: Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper, 2019, Chalmers University of Technology

Consciously, the Maritime Industry / Classification Societies / Marine Engineers / Naval Architects have over the century engaged in progressive research work in the subject area of hull slamming to understand its complexity and the physics behind / underlying it. This is evident owing to the number of publications and literature in this subject area over the decade only. Achieving this global aim will ensure that slamming and slamming induced whipping are incorporated and its effects accounted for in Classification Rules pertaining to structural design and hull integrity in the early stages. Different theories, methods and approaches have been utilized in the various research studies into hull slamming that include momentum theory, boundary element methods, statistical methods, analytical methods computational fluid dynamics – CFD, SPH methods, experimental techniques and full scale experiments. However, each of these methods have limitations and challenges though helping to bridge the gap from what was unknown about slamming in the past to what is being known about the phenomenon in recent times. The future of research and analysis in slamming is through the use of numerical methods most specifically CFD. In view of this, the current research study which is focused on a “Numerical Investigation of the Slamming Event Through FSI Analysis” was carried out by means of a co-simulation using STAR-CCM+, a CFD software and ABAQUS, a FE Software. Investigations were made into the effect of deadrise angles, the effect of the compressibility of air and water (the fluid) and the effect of the magnitude of the water entry velocity / impact velocity. Results from the simulations on the three different focus areas indicate that the unlikely event of slamming / the phenomenon is sensitive to the deadrise angles, compressibility of the fluid and the magnitude of the impact velocity.

Subjects/Keywords: Numerical analysis; FSI analysis; slamming; hull slamming; impact velocity; deadrise angles; compressibility of air; compressibility of water; air cushion.

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Zu, M. A. A. (2019). A Numerical Investigation of the Slamming Event Through FSI Analysis . (Thesis). Chalmers University of Technology. Retrieved from http://hdl.handle.net/20.500.12380/300346

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Zu, Marion Aku Atsine. “A Numerical Investigation of the Slamming Event Through FSI Analysis .” 2019. Thesis, Chalmers University of Technology. Accessed December 09, 2019. http://hdl.handle.net/20.500.12380/300346.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Zu, Marion Aku Atsine. “A Numerical Investigation of the Slamming Event Through FSI Analysis .” 2019. Web. 09 Dec 2019.

Vancouver:

Zu MAA. A Numerical Investigation of the Slamming Event Through FSI Analysis . [Internet] [Thesis]. Chalmers University of Technology; 2019. [cited 2019 Dec 09]. Available from: http://hdl.handle.net/20.500.12380/300346.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Zu MAA. A Numerical Investigation of the Slamming Event Through FSI Analysis . [Thesis]. Chalmers University of Technology; 2019. Available from: http://hdl.handle.net/20.500.12380/300346

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


Indian Institute of Science

3. Akhil, G. Time-Optimal Guidance for Impact Angle Constrained Interception of Moving Targets.

Degree: 2017, Indian Institute of Science

Various unmanned missions deploy vehicles such as missiles, torpedoes, ground robots, and unmanned aerial vehicles. Guidance strategies for these vehicles aim to intercept a target point and satisfy additional objectives such as specifications on impact angle and interception time. Certain impact angles are crucial for a greater warhead effectiveness, and minimizing the interception time is important for vehicles with limited endurance time and for reducing the probability of detection. This thesis considers the time-optimal impact angle constrained guidance problem for interception of moving targets. In the first part of the thesis, a Dubins paths–based guidance methodology for minimum-time lateral interception of a moving and non-maneuvering target is designed. The existence and the time-optimality of the paths are established for impact angle constrained interception of moving targets. The capture regions are analyzed and a classification of the initial geometries is developed for deducing the time-optimal path type. The corresponding guidance command for optimal interception can be generated from the information of initial engagement geometry and target’s speed. In the next part of the thesis, the concept of equivalent virtual target is introduced to address the problem of impact along a general direction. An algorithm is developed to obtain the optimal interception point for generalized interception scenarios. A proof of convergence is presented for the proposed algorithm. Achieving different impact angles, the interceptor often takes sharp turns. Following such curved trajectories, the interceptor may fail to keep the target inside the seeker field-of-view. In the next part of the thesis, the field-of-view characteristics of the proposed optimal guidance strategies are analyzed. Closed-form expressions are derived for the interceptor’s look-angle to the target. Satisfying field-of-view condition at endpoints of the path segments that constitute the optimal path is proven to guarantee target motion inside the field-of-view throughout the engagement. The stationary target case is also analyzed as a specific scenario. The last part of the thesis presents a method to extend the proposed guidance strategies to maneuvering target scenarios. Advisors/Committee Members: Ghose, Debasish, Ratnoo, Ashwini.

Subjects/Keywords: Time-Optimal Guidance; Constrained Interception - Moving Targets; Relative Circular Navigation Guidance; Interception - Moving Targets; Impact Angle Constrained Guidance; Lateral Interception; Impact Angles; Maneuvering Targets; Time-optimal Impact Angle Constrained Paths; Optimal Paths; Dubins Paths; Aerospace Engineering

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Akhil, G. (2017). Time-Optimal Guidance for Impact Angle Constrained Interception of Moving Targets. (Thesis). Indian Institute of Science. Retrieved from http://etd.iisc.ernet.in/2005/3647 ; http://etd.iisc.ernet.in/abstracts/4517/G28472-Abs.pdf

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Akhil, G. “Time-Optimal Guidance for Impact Angle Constrained Interception of Moving Targets.” 2017. Thesis, Indian Institute of Science. Accessed December 09, 2019. http://etd.iisc.ernet.in/2005/3647 ; http://etd.iisc.ernet.in/abstracts/4517/G28472-Abs.pdf.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Akhil, G. “Time-Optimal Guidance for Impact Angle Constrained Interception of Moving Targets.” 2017. Web. 09 Dec 2019.

Vancouver:

Akhil G. Time-Optimal Guidance for Impact Angle Constrained Interception of Moving Targets. [Internet] [Thesis]. Indian Institute of Science; 2017. [cited 2019 Dec 09]. Available from: http://etd.iisc.ernet.in/2005/3647 ; http://etd.iisc.ernet.in/abstracts/4517/G28472-Abs.pdf.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Akhil G. Time-Optimal Guidance for Impact Angle Constrained Interception of Moving Targets. [Thesis]. Indian Institute of Science; 2017. Available from: http://etd.iisc.ernet.in/2005/3647 ; http://etd.iisc.ernet.in/abstracts/4517/G28472-Abs.pdf

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

.