Environmental Response in Coupled Energy and Water Cloud Impact Parameters Derived from A-Train Satellite, ERA-Interim and MERRA-2

Understanding the connections between latent heating from precipitation and cloud radiative effects is essential for accurately parameterizing cross-scale links between cloud microphysics and global energy and water cycles in climate models. While commonly examined separately, this study adopts two cloud impact parameters (CIPs), the surface radiative cooling efficiency, Rc, and atmospheric radiative heating efficiency, Rh, that explicitly couple cloud radiative effects and precipitation to characterize how efficiently precipitating cloud systems influence the energy budget and water cycle using A-Train observations and two reanalyses. These CIPs exhibit distinct global distributions that suggest cloud energy and water cycle coupling are highly dependent on cloud regime. The dynamic regime (ω500) controls the sign of Rh, while column water vapor (CWV) appears to be the larger control on the magnitude. The magnitude of Rc is highly coupled to the dynamic regime. Observations show that clouds cool the surface very efficiently per unit rainfall at both low and high sea surface temperature (SST) and CWV, but reanalyses only capture the former. Reanalyses fail to simulate strong Rh and moderate Rc in deep convection environments but produce stronger Rc and Rh than observations in shallow, warm rain systems in marine stratocumulus regions. While reanalyses generate fairly similar climatologies in the frequency of environmental states, the response of Rc and Rh to SST and CWV results in systematic differences in zonal and meridional gradients of cloud atmospheric heating and surface cooling relative to A-Train observations that may have significant implications for global circulations and cloud feedbacks.

Non-perturbative determination of collisional broadening and medium induced radiation in QCD plasmas

We supply recently obtained results from lattice EQCD with the correct UV limit to construct the collisional broadening kernel C(b⊥) in a QCD plasma. We discuss the limiting behavior of C(b⊥) at small and large impact parameters b⊥, and illustrate how the results can be used to compute medium-induced radiation rates.

Inertial stretching separation in binary droplet collisions

Binary droplet collisions exhibit a wide range of outcomes, including coalescence and stretching separation, with a transition between these two outcomes arising for high Weber numbers and impact parameters. Our experimental study elucidates the effect of viscosity on this transition, which we show exhibits inertial (viscosity-independent) behaviour over an order-of-magnitude-wide range of Ohnesorge numbers. That is, the transition is not always shifted towards higher impact parameters by increasing droplet viscosity, as it might be thought from the existing literature. Moreover, we provide compelling experimental evidence that stretching separation only arises if the length of the coalesced droplet exceeds a critical multiple of the original droplet diameters (3.35). Using this as a criterion, we provide a simple but robust model (without any arbitrarily chosen free parameters) to predict the coalescence/stretching-separation transition.

An Analytical Solution for Non-Linear Viscoelastic Impact

The paper presents an analytical solution for the centric viscoelastic impact of two smooth balls. The contact period has two phases, compression and restitution, delimited by the moment corresponding to maximum deformation. The motion of the system is described by a nonlinear Hunt–Crossley equation that, when compared to the linear model, presents the advantage of a hysteresis loop closing in origin. There is only a single available equation obtained from the theorem of momentum. In order to solve the problem, in the literature, there are accepted different supplementary hypotheses based on energy considerations. In the present paper, the differential equation is written under a convenient form; it is shown that it can be integrated and a first integral is found—this being the main asset of the work. Then, all impact parameters can be calculated. The effect of coefficient of restitution upon all collision characteristics is emphasized, presenting importance for the compliant materials, in the domain of small coefficients of restitution. The results (variations of approach, velocity, force vs. time and hysteresis loop) are compared to two models due to Lankarani and Flores. For quasi-elastic collisions, the results are practically the same for the three models. For smaller values of the coefficient of restitution, the results of the present paper are in good agreement only to the Flores model. The simplified algorithm for the calculus of viscoelastic impact parameters is also presented. This algorithm avoids the large calculus volume required by solving the transcendental equations and definite integrals present in the mathematical model. The method proposed, based on the viscoelastic model given by Hunt and Crossley, can be extended to the elasto–visco–plastic nonlinear impact model.

Theoretical and experimental studies of impact energy and rock-drilling efficiency in vibro-impact drilling

Vibro-impact drilling has been proven to be a viable technique for enhancing the Rate of Penetration (ROP) in deep and ultra-deep well drilling. It is essential to study the effects of impact parameters on impact energy and rock-drilling efficiency for impact tool design and operating parameter optimization. In this paper, the influences of impact parameters including impact frequency, dynamic loading amplitude and loading on impact energy were analyzed by theoretical method. Then a full-scale drilling experiment was conducted to study the rock-drilling efficiency. The results are as follows: the optimal frequency is higher than the resonance frequency of the rock. The impact energy increase with the dynamic loading amplitude. The penetration rate at dynamic loading amplitude of 4 KN (0.13137 mm/s) is 38.7% higher than that of 2 KN (0.09473mm/s). When the impact frequency is lower than150 Hz, the rock-drilling efficiency increases with the impact frequency and dynamic loading amplitude. The penetration rate is 0.1051 mm/s at impact frequency of 150 Hz, which is 29.8% higher than that of 10 Hz. The impact energy and penetration rate at square loading waveform are the largest. The impact energy per second at loading waveform of square, sine and triangular is 19.6 J, 12 J and 7.91 J respectively when the impact frequency is set to optimal frequency of impact energy. This study provides a theoretical guidance for the optimization design of vibro-impact drilling technology.