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- 저자 : Lekkala, Mala Konda Reddy (검색결과 3 건)
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Fatigue damage assessment of offshore riser subjected to vortex-induced vibrations by SHEAR7
Lekkala Malakonda Reddy,Latheef Mohamed,Jung Jae Hwan,Kim Young Tae,김도균 대한조선학회 2022 International Journal of Naval Architecture and Oc Vol.14 No.1
Marine risers are a critical component in transporting the produced hydrocarbons from the seabed to the topside facility and vice versa. These risers are subjected to VIV when encountered with ocean currents, leading to the accumulation of fatigue damage, which reduces the risers' service life. Estimation of fatigue damage is an important aspect to assure reliable and operable conditions. SHEAR7 is used in this analysis to estimate the fatigue damage of the Top Tensioned Riser (TTR). SHEAR7 is widely used semiempirical software in the offshore industry to estimate the fatigue damage induced by VIV. Recently, SHEAR7 has been revised to account for the higher harmonic corrections based on experimental and field data. The key pertaining to the revision of adding higher harmonics can contribute 50% higher strain along the length of the riser at some locations (Jhingran and Vandiver, 2007). VIV fatigue damage analysis was conducted using SHEAR7 v4.7b and v4.9b to investigate the effect of the higher harmonics considered in the later version. The TTR model used in this analysis was modelled in OrcaFlex and validated with available references in the literature. TTR with different model scenarios was developed, and comparisons were made between the predicated responses from SHEAR7 v4.b and v4.9b for the riser. It was observed that higher harmonic correction factors have a great impact on the performance of the riser. Finally, sensitivity analyses were carried out to check the effect of individual parameters and higher harmonic correction factors on predicted responses between the two versions of SHEAR7.
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A parametric study on fatigue of a top-tensioned riser subjected to vortex-induced vibrations
Kim, Do Kyun,Wong, Eileen Wee Chin,Lekkala, Mala Konda Reddy Techno-Press 2019 Structural monitoring and maintenance Vol.6 No.4
This study aims to provide useful information on the fatigue assessment of a top-tensioned riser (TTR) subjected to vortex-induced vibration (VIV) by performing parametric study. The effects of principal design parameters, i.e., riser diameter, wall thickness, water depth (related to riser length), top tension, current velocity, and shear rate (or shear profile of current) are investigated. To prepare the base model of TTR for parametric studies, three (3) riser modelling techniques in the OrcaFlex were investigated and validated against a reference model by Knardahl (2012). The selected riser model was used to perform parametric studies to investigate the effects of design parameters on the VIV fatigue damage of TTR. From the obtained comparison results of VIV analysis, it was demonstrated that a model with a single line model ending at the lower flex joint (LFJ) and pinned connection with finite rotation stiffness to simulate the LFJ properties at the bottom end of the line model produced acceptable prediction. Moreover, it was suitable for VIV analysis purposes. Findings from parametric studies showed that VIV fatigue damage increased with increasing current velocity, riser outer diameter and water depth, and decreased with increasing shear rate and top tension of riser. With regard to the effects of wall thickness, it was not significant to VIV fatigue damage of TTR. The detailed outcomes were documented with parametric study results.
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Bommisetty Reddyyamini,Chakravartty Navajeet,Hariprasad K. R.,Rameshbabu P.,Sudhakar P.,Bodanapu Reddaiah,Naik Jeevula Bhukya,Reddy B. V. Bhaskar,Lekkala Sivrama Prasad,Gupta Saurabh,Tanti Bhaben,Lach 한국식물생명공학회 2023 Plant biotechnology reports Vol.17 No.2
The grain number is one of the highly complex and crucial traits determining the grain yield in rice. To identify grain number QTLs in rice, we employed the QTL-seq approach in the 297 F2 population derived from the cross between BPT5204 and NLR33892. In this investigation, five regions viz., qGN1, qGN3, qGN7, qGN9, and qGN12 on chromosomes 1,3,7,9, and 12, respectively, were identified as QTLs governing grain number per panicle in rice. To verify the QTLs identified in the present study, traditional QTL mapping was carried out using InDel markers and previously reported SSRs in the QTL region. From qGN12 QTL, RM6953 showed a significant association with the number of grains per panicle with a phenotypic variance of 24.58, 22.10, and 17.20% in F2, F2:3, and BC1F2 populations, respectively, at < 0.0001 P value, indicating major QTL. From genome resequencing data, a missense variance was observed in the exonic region of LOC_Os12g39330 gene controlling AP2 domain-containing protein which plays an important role in seed development in rice. Hence, this QTL can be a potential target for map-based cloning and marker-assisted transfer to enhance the grain number in rice.
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