Search or add a thesis

Advanced Search (Beta)
Home > Numerical Simulations, Nonlinear Analysis and Control of Bio-Inspired Flows: A Step Towards Autonomous Vehicles

Numerical Simulations, Nonlinear Analysis and Control of Bio-Inspired Flows: A Step Towards Autonomous Vehicles

Thesis Info

Access Option

External Link

Author

Khalid, Muhammad Saif Ullah

Program

PhD

Institute

National University of Sciences & Technology

City

Islamabad

Province

Islamabad

Country

Pakistan

Thesis Completing Year

2016

Thesis Completion Status

Completed

Subject

Applied Sciences

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/7302/1/Muhammad_Saif_Ullah_Khalid_Mechanical_Engineering_2016_NUST_HSR_22.08.2016.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676726779336

Similar


To propose e cient and better designs for small swimming and ying unmanned vehicles, understanding of the unsteady mechanisms to generate lift and thrust forces at low Reynolds numbers is of key importance. Fluid owing over these vehicles interact nonlinearly with the structure and carries great complexities. Recently, due to interest in biomimicking ying (micro-air vehicles) and swimming robots (underwater vehicles), industry has shown keen interest in production of these vehicles. To design e ective control of these vehicles, thorough understanding of its unsteady aerodynamics and underlying phenomena is required. In this study, we focus upon coupling the numerical simulations with the tools of nonlinear dynamics. We decompose this whole study into two parts; aerodynamics and hydrodynamics. In therst part, we investigate the bifurcations occurring in the ows over oscillating airfoils at low Reynolds numbers. Investigation of mechanism responsible for the generation of unsteady forces pose challenges due to wide spectrum of parameters that are involved in its dynamics. Both experimental and currently available numerical techniques require costly resources in terms of time and money. Considering this fact, we also develop nonlinear reduced-order models for unsteady aerodynamic forces produced by plunging, pitching, and apping airfoils. Observing similarity in the character of unsteady forces generated by pitching, and plunging airfoils, we propose an equivalence criteria to obtain the aerodynamic forces of same magnitude or order. We also demonstrate that de ection of the wake for large Strouhal numbers is a result of strong quadratic nonlinearity. With the lessons learnt from the nonlinear analysis/interaction of apping airfoils, we investigate the hydrodynamics ofsh swimming in the second part of this dissertation. We consider a singlesh and twosh in tandem performing traveling-wave like motion, known as undulation. In case of tandem con guration, we numerically simulate the ow while both sh undulate asynchronously. We quantify the drafting and inverse-drafting e ects using time-averaged drag coe cients. We also explain physical mechanisms which are responsible for hydrodynamic advantage/disadvantage to upstream and downstreamsh. To further enhance our understanding related to the instability mechanisms in the wakes of undulating bodies, we compute the symmetry/asymmetry of parent and combined modes. We apply the symmetry principles, already established for drag-producing wakes of blubodies, to the thrust-producing wakes of undulatingsh. We conclude that thrust producing wakes also follow the same symmetry principles. This research addresses the coupling of techniques/tools of nonlinear mechanics with computational uid dynamics to explore important features of complex ows around oscillating and undualating bodies.
Loading...
Loading...

Similar Books

Loading...

Similar Chapters

Loading...

Similar News

Loading...

Similar Articles

Loading...

Similar Article Headings

Loading...

مرشیہ مرشد پاک

مرثیہ مرشد پاک
(مرثیہ جو مرشد پاک کے وصال کے بعد دربار پر حاضری کے وقت پڑھا گیا )

تان ساڑھی وچ ماڑی سوں گیوں دلدار وے
عاشق خالی ویکھ حجرہ رون ڈھائیں مار وے

سخن تیرے یاد کرکے رون زارو نذار وے
نکل آ، لا محفلاں، توں آ سُہا دربار وے

کون دیسی آن تسلیاں شہزادیاں نوں یار وے
کون دھرسی ہتھ سر تے ‘ کون کرسی پیار وے

عاشقاں دربار ملّا رون سانگاں مار وے
کد ملسی یار سوہنا بنھ کے دستار وے

حضورمحمد فیض علی شاہ ہَے نام سوہنا دل دیندا ٹھار وے
عاشقاں نے تانگ رکھی آ کرادے دیدار وے

سنج کچہری کر چلے عاشقاں سالار وے
باہجھ دلبر یار جانی جیونا بیکار وے

ویکھ جگہ مجلس والی نین مینہ برسائوندے
کتھ گئے دلدار جانی جیہڑے رونقاں لائوندے

باغ تیرا ذکر والا باہجھ تیرے سکیا
قمر نوری حسن والا ہیٹھ بدلی لکیا

نین کجلے دار تیرے عاشقاں من بھائوندے
حسن والے مان کردے عاشقاں ترسائوندے

اے محبوبا ویکھ تینوں نین کدی نہ رجدے
نوری مکھڑا حسن بھریا زلفاں کنڈل پھبدے

قادری سائیںؔ مرشد دے در رو رو ہاڑے پائوندا
باہجھ تیرے اے محبوبا چین نہ ہے آئوندا

Peran Guru Dalam Membentuk Karakter Siswa Di SMA Swasta Katolik Bintang Laut

Saat ini dalam dunia pendidikan khususnya dalam bidang karakter yang dimiliki oleh siswa, seringkali siswa melalaikan karakter yang harusnya siswa tanamkan dalam dirinya. Dalam menyikapi hal tersebut maka peranan guru sangat penting didalamnya. Tujuan penelitian ini adalah untuk mengetahui peranan guru dalam membentuk karakter siswa di SMAS Katolik Bintang Laut, bagaimana profesionalisme guru dan budaya sekolah dapat berpengaruh dalam membentuk karakter siswa. Pendekatan yang dilakukan dalam penelitian ini adalah pendekatan kualitatif dengan jenis penelitian deskriptif. Sumber data dalam penelitian ini adalah guru di SMAS Katolik Bintang Laut, sampel 5 orang Guru sebagai responden dan 5 orang siswa sebagai informan. Teknik pengumpulan data yang dilakukan adalah melalui tahap observasi, wawancara dan dokumentasi. Analisis data yang dilakukan melalui tiga alur kegiatan (1) Reduksi data, (2) Penyajian data, (3) Penarikan kesimpulan. Hasil peneliti menunjukkan bahwa peranan guru sangat penting dalam membentuk karakter siswa di SMAS Katolik Bintang Laut, hampir semua guru profesional dalam melaksanakan tugasnya, memberikan contoh dan teladan yang baik, seperti datang tepat waktu, berpakaian rapi, bertanggungjawab atas apa yang sudah dipercayakan padanya, serta memberikan teguran dan sanksi bagi siswa yang melalaikan tanggung jawabnya, adapun budaya sekolah di SMAS Katolik Bintang Laut yaitu ada apel setiap pagi dengan bernyanyi dan berdoa bersama serta pembacaan renungan singkat, senam pagi setiap hari Jumat, dan misa awal bulan.

Theoretical Analysis of the Effect of Defects on Physical Properties of Ii-Vi Semiconductors

The ability to obtain tunable properties in semiconductor devices with compositional variation makes multi-ternary semiconductor compounds extremely useful for a variety of industrial applications such Solar Cells, Light Emitting Diodes (LED), X-rays and Gamma ray detectors. II-VI semiconductors have attracted great attention due to their interesting applications in everyday life and research. In this thesis, the physical properties of II-VI pure and their multi-ternary compounds with the zinc-blende phase are explored. To calculate the physical properties of ZnO1-xSx, ZnSe1-xSx and CdSe1-xSx by introducing defects using plane wave pseudo-potential method with Local Density Approximation (LDA) and LDA+U. The obtained results of each individual compound are given below. In ZnO1-xSx crystal, Sulfur is replaced by Oxygen in the step of 0.25 from 0 to 1. The variance in the structural, electronic, and thermodynamic properties of ZnO1-xSx semiconductors with the change in doping concentration of Sulfur are calculated. It is observed that the LDA+U method gives better improvement in the results instead of LDA. At various concentrations the ground-state properties are determined for bulk materials ZnO, ZnS, and their tertiary alloys in cubic zinc-blende phase. From the results, a minor difference has been observed in lattice parameters from Vegard‟s law and other calculated results which may be due to the large mismatch of lattice parameters of binary compounds ZnO and ZnS. A small deviation in the bulk modulus from linear concentration dependence has also observed for these alloys. The thermodynamic properties including the phonon contribution to Helmholtz free energy ΔF, phonon contribution to internal energy ΔE, and specific heat at constant-volume CV are calculated within quasi harmonic approximation based on the calculated phonon dispersion relations. The structural, electronic, and elastic properties of ZnSe1-xSx for zinc-blende structure with different composition are calculated. The exchange-correlation potential is treated with the pz-LDA for these properties. Moreover, LDA+U approximation is employed to treat the “d” orbital electrons properly. A comparative analysis of band gap calculated within both LDA and LDA+U schemes is presented. The analysis of obtained results shows considerable improvement in the band gap. The inclusion of compositional disorder increases the values of all elastic constants. The results have shown that elastic Page ix constant C11, C12, and C44 are mainly influenced by compositional disorder and found to be in well agreement with literature. The results also reflect the ductile nature of these pure and defected alloys. The ground-state properties are resolute for the bulk materials CdS, CdSe, and their alloys. Very small deviation of the lattice constant from Vegard‟s law is observed for CdSe1–xSx alloys at different concentrations but a little larger deviation of the bulk modulus from linear concentration dependence (LCD) is observed for considered alloy with downward bowing. The effect of Sulfur composition on electronic properties using LDA and LDA+U is explored. It is found that with LDA+U method, the band gap for CdSe1–xSx is very close to experimental value. Elastic constants such as C11, C12, C44, Young Modulus, and Shear Modulus are also calculated and these results revealed that CdSe1–xSx compound is ductile in nature.