126 research outputs found
Master-modes in 3D turbulent channel flow
Turbulent flow fields can be expanded into a series in a set of basic
functions. The terms of such series are often called modes. A master- (or
determining) mode set is a subset of these modes, the time history of which
uniquely determines the time history of the entire turbulent flow provided that
this flow is developed. In the present work the existence of the
master-mode-set is demonstrated numerically for turbulent channel flow. The
minimal size of a master-mode set and the rate of the process of the recovery
of the entire flow from the master-mode set history are estimated. The velocity
field corresponding to the minimal master-mode set is found to be a good
approximation for mean velocity in the entire flow field. Mean characteristics
involving velocity derivatives deviate in a very close vicinity to the wall,
while master-mode two-point correlations exhibit unrealistic oscillations. This
can be improved by using a larger than minimal master-mode set. The near-wall
streaks are found to be contained in the velocity field corresponding to the
minimal master-mode set, and the same is true at least for the large-scale part
of the longitudinal vorticity structure. A database containing the time history
of a master-mode set is demonstrated to be an efficient tool for investigating
rare events in turbulent flows. In particular, a travelling-wave-like object
was identified on the basis of the analysis of the database. Two
master-mode-set databases of the time history of a turbulent channel flow are
made available online at http://www.dnsdata.afm.ses.soton.ac.uk/. The services
provided include the facility for the code uploaded by a user to be run on the
server with an access to the data
Large-eddy simulation of the interaction of a jet with a wing
This paper presents progresses made on aircraft installation effects using numerical methods under WP 3.2 of SYMPHONY, a project supported by Technology Strategy Board, UK. Large-eddy simulations (LES) were performed for turbulent flow around a wing under the influence from engine jet flow by solving the compressible Navier-Stokes equations using an in-horse high-order finite difference code. Simulations were performed for jet under both a clean wing and the wing at high-lift configuration. Installation effects on both the jet and the wing are analysed by comparing with LES results performed for three baseline cases: jet along, clean wing along and the wing in high-lift configuration. It is found that the flow is two-dimensional near the leading edge of the wing. Further down-stream three-dimensional flow features are developed. Interaction with vortical jet stream accelerates developments of the flow underneath the wing. Stronger turbulent structures are seen within the jet shear layer near the wing and their interaction with the wing causes surface pressure fluctuations, which results in increased radiated noise. Interaction with the jet causes a reduction in lift for the clean wing, however the contribution from the flap is increased when the wing is in high-lift configuration. For the current geometry the jet stream does not hit the clean wing, and it is shifted towards the wing by a small angle (one degree) due to low pressure region under the wing. When the ap is deployed, jet stream hits the flap and is deflected away from the wing
Sensitivity of the intensity frontier experiments for neutrino and scalar portals: analytic estimates
In recent years, a number of intensity-frontier experiments have been
proposed to search for feebly interacting particles with a mass in the GeV
range. We show analytically how the characteristic shape of the sensitivity
regions of such experiments - upper and lower boundaries of the probed region,
the maximal mass reach - depends on the parameters of the experiments, taking
the SHiP and the MATHUSLA experiments as an example. We find a good agreement
of our estimates with the results of the Monte Carlo simulations.Comment: Journal versio
Probing new physics with displaced vertices: muon tracker at CMS
Long-lived particles can manifest themselves at the LHC via "displaced
vertices" - several charged tracks originating from a position separated from
the proton interaction point by a macroscopic distance. Here we demonstrate a
potential of the muon trackers at the CMS experiment for displaced vertex
searches. We use heavy neutral leptons and Chern-Simons portal as two examples
of long-lived particles for which the CMS muon tracker can provide essential
information about their properties.Comment: Journal versio
Sensitivity of the FACET experiment to Heavy Neutral Leptons and Dark Scalars
We analyze the potential of the recently proposed experiment FACET (Forward-Aperture CMS ExTension) to search for new physics. As an example, we consider the models of Higgs-like scalars with cubic and quartic interactions and Heavy Neutral Leptons. We compare the sensitivity of FACET with that of other proposed “intensity frontier” experiments, including FASER2, SHiP, etc. and demonstrate that FACET could probe an interesting parameter space between the current constraints and the potential reach of the above mentioned proposals
Phenomenology of GeV-scale scalar portal
We review and revise the phenomenology of the scalar portal -- a new scalar
particle with the mass in GeV range that mixes with the Higgs boson. In
particular, we consider production channels and and show that their contribution is significant. We extend the
previous analysis by comparing the production of scalars from decays of mesons,
of the Higgs bosons and direct production via proton bremsstrahlung, deep
inelastic scattering and coherent scattering on nuclei. Relative efficiency of
the production channels depends on the energy of the beam and we consider the
energies of DUNE, SHiP and LHC-based experiments. We present our results in the
form directly suitable for calculations of experimental sensitivities.Comment: Journal versio
Sensitivities to feebly interacting particles: public and unified calculations
The idea that new physics could take the form of feebly interacting particles
(FIPs) - particles with a mass below the electroweak scale, but which may have
evaded detection due to their tiny couplings or very long lifetime - has gained
a lot of traction in the last decade, and numerous experiments have been
proposed to search for such particles. It is important, and now very timely, to
consistently compare the potential of these experiments for exploring the
parameter space of various well-motivated FIPs. The present paper addresses
this pressing issue by presenting an open-source tool to estimate the
sensitivity of many experiments - located at Fermilab or at the CERN's SPS,
LHC, and FCC-hh - to various models of FIPs in a unified way: the
Mathematica-based code SensCalc
Sensitivities to feebly interacting particles: public and unified calculations
The idea that new physics could take the form of feebly interacting particles (FIPs) - particles with a mass below the electroweak scale, but which may have evaded detection due to their tiny couplings or very long lifetime - has gained a lot of traction in the last decade, and numerous experiments have been proposed to search for such particles. It is important, and now very timely, to consistently compare the potential of these experiments for exploring the parameter space of various well-motivated FIPs. The present paper addresses this pressing issue by presenting an open-source tool to estimate the sensitivity of many experiments - located at Fermilab or at the CERN\u27s SPS, LHC, and FCC-hh - to various models of FIPs in a unified way: the Mathematica-based code SensCalc
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