230,083 research outputs found
On the structure and origin of pressure fluctuations in wall turbulence: predictions based on the resolvent analysis
No full textWe generate predictions for the fluctuating pressure field in turbulent pipe flow by re-formulating the resolvent analysis of McKeon & Sharma (2010) in terms of the so-called primitive variables. Under this analysis, the nonlinear convective terms in the Fourier-transformed Navier-Stokes equations are treated as a forcing that is mapped to a velocity and pressure response by the resolvent of the linearized Navier-Stokes operator. At each wavenumber-frequency combination, the turbulent velocity and pressure field are represented by the most-amplified (rank-1) response modes, identified via a singular value decomposition of the resolvent. We show that these rank-1 response modes reconcile many of the key relationships between the velocity field, coherent structure (i.e., hairpin vortices), and the high-amplitude wall-pressure events observed in previous experiment and DNS. A Green’s function representation shows that the pressure fields obtained under this analysis correspond primarily to the fast pressure contribution arising from the linear interaction between the mean shear and the turbulent wall-normal velocity. Recovering the slow pressure requires an explicit treatment of the nonlinear interactions between the Fourier response modes. By considering the velocity and pressure fields associated with the triadically-consistent mode combination studied by Sharma & McKeon (2013), we identify the possibility of an apparent amplitude modulation effect in the pressure field, similar to that observed for the streamwise velocity field. However, unlike the streamwise velocity, for which the large scales of the flow are in phase with the envelope of the small-scale activity close to the wall, we expect there to be a ?/2 phase difference between the large scale wall-pressure and the envelope of the small-scale activity. Finally, we generate spectral predictions based on a rank-1 model assuming broadband forcing across all wavenumber-frequency combinations. Despite the significant simplifying assumptions, this approach reproduces trends observed in previous DNS for the wavenumber spectra of velocity and pressure, and for the scale-dependence of wall-pressure propagation speed
Dr. Sharma Lasers
No full textDr. Suresh C. Sharma, professor of physics, poses in front of students working with lasers in a lab.https://mavmatrix.uta.edu/utalibraries_digitalprojects_universityphotos/1409/thumbnail.jp
Cacopsylla longigena Burckhardt & Sharma & Raman 2018, comb. nov.
No full textCacopsylla longigena (Mathur, 1975), comb. nov. Distribution. India (Hodkinson 1986): West Bengal (Mathur 1975, as Psylla longigena). Host plant. Exbucklandia populnea (Hamamelidaceae). Comments. Originally described in Psylla, this species is not congeneric with Psylla alni (Linnaeus, 1758), the type species of Psylla. For this reason, it is formally transferred here to Cacopsylla as C. longigena (Mathur, 1975), comb. nov. from Psylla.Published as part of Burckhardt, Daniel, Sharma, Anamika & Raman, Anantanarayanan, 2018, Checklist and comments on the jumping plant-lice (Hemiptera: Psylloidea) from the Indian subcontinent, pp. 1-38 in Zootaxa 4457 (1) on page 19, DOI: 10.11646/zootaxa.4457.1.1, http://zenodo.org/record/145753
Cacopsylla shillongensis Burckhardt & Sharma & Raman 2018, comb. nov.
No full textCacopsylla shillongensis (Lahiri & Biswas, 1990), comb. nov. Distribution. India: Megalaya (Lahiri & Biswas 1990, as Psylla shillongensis). Host plant. Unknown. Comments. Originally described in Psylla, this species is not congeneric with Psylla alni (Linnaeus, 1758), the type species of Psylla. For this reason, it is formally transferred here to Cacopsylla as C. shillongensis (Lahiri & Biswas, 1990), comb. nov. from Psylla.Published as part of Burckhardt, Daniel, Sharma, Anamika & Raman, Anantanarayanan, 2018, Checklist and comments on the jumping plant-lice (Hemiptera: Psylloidea) from the Indian subcontinent, pp. 1-38 in Zootaxa 4457 (1) on page 20, DOI: 10.11646/zootaxa.4457.1.1, http://zenodo.org/record/145753
Opposition control within the resolvent analysis framework
No full textThis paper extends the resolvent analysis of McKeon & Sharma (2010) to consider flow control techniques that employ linear control laws, focusing on opposition control (Choi et al. 1994) as an example. Under this formulation, the velocity field for turbulent pipe flow is decomposed into a series of highly amplified (rank-1) response modes, identified from a gain analysis of the Fourier-transformed Navier-Stokes equations. These rank-1 velocity responses represent propagating structures of given streamwise/spanwise wavelength and temporal frequency, whose wall-normal footprint depends on the phase speed of the mode. Opposition control, introduced via the boundary condition on wall-normal velocity, affects the amplification characteristics (and wall-normal structure) of these response modes; a decrease in gain indicates mode suppression, which leads to a decrease in the drag contribution from that mode. With basic assumptions, this rank-1 model reproduces trends observed in previous DNS and LES, without requiring high-performance computing facilities. Further, a wavenumber-frequency breakdown of control explains the deterioration of opposition control performance with increasing sensor elevation and Reynolds number. It is shown that slower-moving modes localized near the wall (i.e. attached modes) are suppressed by opposition control. Faster-moving detached modes, which are more energetic at higher Reynolds number and more likely to be detected by sensors far from the wall, are further amplified. These faster-moving modes require a phase lag between sensor and actuator velocity for suppression. Thus, the effectiveness of opposition control is determined by a trade-off between the modes detected by the sensor. However, it may be possible to develop control strategies optimized for individual modes. A brief exploration of such mode-optimized control suggests the potential for significant performance improvement
Paktongius thaiensis Klementz & Sharma 2023, comb. nov.
No full text<i>Paktongius thaiensis</i> (Suzuki, 1985) comb. nov. <p> <i>Mysorea thaiensis</i> Suzuki, 1985, p. 102 –104, fig. 19, Table 15; Zhang & Zhang, 2015, p. 336 –341, figs. 1–25, table 1.</p> <p> <i>Material examined.</i> ♂ (MCZ-92256/ MCZ DNA104859) THAILAND, Sakon Nakhon, Phu Phan National Park (16°48.63’N, 103°53.59’E), 1-4.vi. 2007, 522 m, dry evergreen forest near house, <i>leg.</i> W. Kongnara.</p> <p> <i>Diagnosis.</i> Distinguished from congeners by the combination of the following characters: (1) anal plate with three large spines; (2) free tergite III with a transverse row of six tubercles; (3) scutal areas II-V with two median tubercles at posterior margin; (4) tarsal formula 5:9:6:6.</p> <p> <i>Distribution.</i> Known from: Chiang Mai (Suzuki 1985) and Sakon Nakhon Provinces, Thailand; Champasak Province, Laos (Zhang & Zhang 2015) (Fig. 12).</p>Published as part of <i>Klementz, Benjamin C. & Sharma, Prashant P., 2023, New species of Paktongius and convergent evolution of the gonyleptoid-like habitus in Southeast Asian Assamiidae (Opiliones: Laniatores), pp. 34-54 in Zootaxa 5389 (1)</i> on page 51, DOI: 10.11646/zootaxa.5389.1.2, <a href="http://zenodo.org/record/10404551">http://zenodo.org/record/10404551</a>
Paratylenchus prunii Sharma, Sharma & Khan 1986
No full text<i>Paratylenchus prunii</i> Sharma, Sharma & Khan, 1986 Esmaeili & Heydari 2017: <p> 10♀: L = 324 (290–343) µm; <i>a</i> = 21.8 (20.3–23.2); <i>b</i> = 3.1 (3.0–3.5); <i>c</i> = 12.8 (10.7–17.5); St = 26.1 (24.0– 28.0) µm; V = 81 (79–83)</p> <p> 2♂: L = 275, 290 µm; <i>a</i> = 19.3, 21.2; <i>c</i> = 12.6, 13.8; Spicules = 14, 15 µm</p> <p>Associated plant and locality: Grapevine from Kermanshah (Esmaeili & Heydari 2 0 17 [F])</p>Published as part of <i>Ghaderi, Reza, Karegar, Akbar, Miraeiz, Esmaeil & Hesar, Abbas Mokaram, 2019, An updated and annotated checklist of the Tylenchulidae (Nematoda: Criconematoidea) of Iran, pp. 205-229 in Zootaxa 4545 (2)</i> on page 213, DOI: 10.11646/zootaxa.4545.2.3, <a href="http://zenodo.org/record/2618787">http://zenodo.org/record/2618787</a>
Myrmica longisculpta Bharti & Sharma 2011, sp. nov.
No full textMyrmica longisculpta sp. nov. (Figs. 1–3; Table 1) Type material. HOLOTYPE: Worker, INDIA: JAMMUAND KASHMIR: Sarthal, 32.812947°N, 75.762503°E, 2200m a.s.l., 15.vi. 2009 (coll. Sharma, Punjabi University). PARATYPES: 4 workers, with same data as of holotype, not from same nest; 1 worker, INDIA: JAMMU AND KASHMIR: Machedi, 32.72364°N, 75.669464°E, 2000 m a.s.l., 3.viii.2008 (coll. Sharma) and 1 worker, INDIA: JAMMU AND KASHMIR: Shopian, 33.668354°N, 74.779472°E, 3100 m a.s.l., 12.ix.2009 (coll. Sharma). One paratype will be deposited in Natural History Museum, London. Description. Head much longer than broad, sides parallel, occipital margin straight; mandibles with 8 teeth (apical and preapical are the largest); clypeus convex, anterior clypeal margin prominent and somewhat pointed medially and extending over mandibles, posterior margin clear, broad, extending between antennal bases; frontal carinae short, slightly broader anteriorly than posteriorly and curving outwards to merge with rugae that surround the antennal socket (in three paratype workers frontal carina of one side merges with rugae that surround antennal insertions); antennae 12 segmented; scape slender, narrow, weakly curved at base without any trace of lobe or carina, widening towards apex, just extending beyond the upper margin of head, antennae with oblique short hairs having pubescence on apical 3 segments; eyes large, placed almost at midline of head; head covered with numerous interspersed short and long suberect hairs; mandibles and clypeus also equipped with long suberect hairs. Alitrunk dorsum feebly convex; promesonotal suture indistinct; metanotal groove broad, shallow; propodeal lobes rounded apically; propodeal spines long, sharp, projected backward, divergent; tibiae of hind and middle legs with well developed pectinate spur; petiole longer than broad, with very short anterior peduncle with a tooth like subpetiolar process, post-petiole a little longer than broad; promesonotum with long erect, as well as short hairs; propodeum with 1 to 2 pairs of short suberect hairs; petiole and post-petiole equipped with long and short suberect hairs directed backwards. Gaster with numerous long erect to suberect hairs, and with few short suberect hairs between them. Punturation. Head longitudinally rugulose with punctures; clypeus convex, longitudinally rugulose, space between rugae smooth and shiny; frontal triangle highly polished and shiny; all antennal segments densely punctuated except scape, first 2 segments are minutely punctated; cephalic dorsum longitudinally rugose up to vertex behind which it is reticulated; whole of the alitrunk distinctively longitudinally coarsely rugose with much pronounced rugae; the pronotum dorsum with somewhat broken longitudinal sculpture; the lateral parts of the body with distinct longitudinal rugae, as does the petiole and post-petiole dorsum; gaster smooth, highly polished and shiny. Male and female unknown. Differential diagnosis. Myrmica longisculpta sp. nov. most resembles species that Radchenko & El mes (2010) placed in the rugosa complex of the M. rugosa species group, which have frontal carinae merging with rugae that extend to occipital margin of head. The coarse body sculpture with the presence of very pronounced/elevated longitudinal rugae on the alitrunk clearly separates it from allied species (including Myrmica afghanica Radchenko & Elmes, 2003, which is not assigned to any species-group). It most resembles Myrmica rugosa Mayr, 1865 but has a relatively wider frontal lobe and a petiole with longitudinal rugae than that species. The fact that some specimens in part appear to have frontal carinae that merge with rugae that surround antennal sockets is problematic. This is a very distinctive species group character which discriminates the smythiesii group from allied groups. However Myrmica longisculpta sp. nov. is most unlikely to be in the smythiesii species group, species of which are generally small with weak sculpture. Moreover the exact placement of this species in a particular group will become clearer when males are found. Etymology. Named in reference to the presence of deep longitudinal sculpture on the alitrunk. Ecology. The species has been hand-collected from two localities (Sarthal, 32.812947°N, 75.762503°E, 2200 m a.s.l and Shopian, 33.668354°N, 74.779472°E, 3100 m a.s.l.) and from leaf litter using Winkler’s extractor at another locality (Machedi, 32.72364°N, 75.669464°E, 2000 m a.s.l.). The collection site at Machedi has a patchy Cedrus forest along with agricultural land surrounding the site; moreover the area has a lot of anthropogenic activities with dry type of environment (mean temperature during collection period 32°C, relative humidity 36.62 % and thickness of leaf litter 2.1 cm). The collection site at Sarthal has dense Cedrus forest with abundant leaf litter and no agricultural land. It remains snow clad from November to the beginning of March and has very limited anthropogenic activities with only nomads visiting the area (mean temperature during collection period 22°C, relative humidity 66.38 %, thickness of leaf litter 3.9 cm) with a comparatively wet environment. At the third collection site (Shopian) specimens were collected under a stone. The area has scattered Cedrus trees, as the forest has largely been cleared by human activities (mean temperature during collection period was 22°C and relative humidity 54 %). The ecology of the Himalaya is temperature-dependent. The snow line occurs at an average of 6000 meters above sea level and the average altitude at which the forest disappears is 3000 meters. Two of the habitats (Machedi and Sarthal) represent the transitional zone between subtemperate and temperate Himalaya whereas the more northerly and higher Shopian site penetrates into the Palaearctic zone whose boundary in Southern Asia is largely altitudinal (where an altitude of 2000–2500 meters above sea level forms the boundary between Palaearctic and Indo-Malayan ecozones). At this altitude the microclimate plays an important role for ants like Myrmica which prefer to live under stones or in rare cases in leaf litter, because the soil temperature is comparatively higher than ambient temperature in these microhabitats (BHARTI 2008b). Distribution. Himalaya (India: Jammu and Kashmir).Published as part of Bharti, Himender & Sharma, Yash Paul, 2011, Myrmica longisculpta, a new species from Himalaya (Hymenoptera: Formicidae: Myrmicinae), pp. 723-729 in Acta Entomologica Musei Nationalis Pragae 51 (2) on pages 725-729, DOI: 10.5281/zenodo.532980
Claraeola thekkadiensis Kapoor, Grewal & Sharma 1987, comb. nov.
No full textClaraeola thekkadiensis (Kapoor, Grewal & Sharma, 1987)comb. nov. Eudorylas thekkadiensis Kapoor, Grewal & Sharma, 1987:111 Examined materal. Holotype. • ♂; Thekkady (Kerala); 24 Feb. 2019; J.S. Grewal; Allotype. • 1♀; same data as holotype; S.K. Sharma. Paratype. • 2♂♂; same data as holotype • 3♂♂; Ramgrah (Bihar); 22 Mar. 1958; S.K. Sharma • 2♀♀; Ranchi (Bihar); 22 Mar. 1985; V.K. Kohli • 1♂; Ranikhet (U.P.); 8 Oct. 1985; S.K. Sharma; Depository: all INPC. Distribution. India. Remarks. Although not a Middle Eastern species, this is similar to C. mantisphalliga so relevant to this paper. From the detailed drawings of the male genitalia included in the original description (Kapoor et al. 1987), the taxon is transferred from Eudorylas to the Claraeola.Published as part of Motamedinia, Behnam, Skevington, Jeffrey H. & Kelso, Scott, 2019, Revision of Claraeola (Diptera, Pipunculidae) in the Middle East based on morphology and DNA barcodes, pp. 85-111 in ZooKeys 873 on page 85, DOI: 10.3897/zookeys.873.3664
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