采煤机摇臂水道结构对换热效果的影响分析

为研究采煤机摇臂冷却水道结构对散热效率的影响,提高采煤机摇臂冷却水道的散热效率,通过Fluent数值计算方法对不同结构冷却水道的温度场、压力场进行数值分析。结果表明:随着流速增加,Nu随之增加,对流换热效率提高;波高会增加流体扰动强化换热效果,同时转角流动死区也会降低换热效果,在h=15 mm换热效率最佳;波间距越小,水道转角数量越多,增大压降,但流道长度增加,流体携带的热量会增加。

Oblique Water Wave Scattering by Bottom Undulation in a Two-layer Fluid Flowing Through a Channel

The problem of oblique wave （internal wave） propagation over a small deformation in a channel flow consisting of two layers was considered. The upper fluid was assumed to be bounded above by a rigid lid, which is an approximation for the free surface, and the lower one was bounded below by an impermeable bottom surface having a small deformation; the channel was unbounded in the horizontal directions. Assuming irrotational motion, the perturbation technique was employed to calculate the first-order corrections of the velocity potential in the two fluids by using Green＇s integral theorem suitably with the introduction of appropriate Green＇s functions. Those functions help in calculating the reflection and transmission coefficients in terms of integrals involving the shape ftmction c（x） representing the bottom deformation. Three-dimensional linear water wave theory was utilized for formulating the relevant boundary value problem. Two special examples of bottom deformation were considered to validate the results. Consideration of a patch of sinusoidal ripples （having the same wave number） shows that the reflection coefficient is an oscillatory function of the ratio of twice the x-component of the wave number to the ripple wave number. When this ratio approaches one, the theory predicts a resonant interaction between the bed and the interface, and the reflection coefficient becomes a multiple of the number of ripples. High reflection of incident wave energy occurs if this number is large. Similar results were observed for a patch of sinusoidal ripples having different wave numbers. It was also observed that for small angles of incidence, the reflected energy is greater compared to other angles of incidence up to π/ 4. These theoretical observations are supported by graphical results.

An Assessment of MJO and Tropical Waves Simulated by Different Versions of the GAMIL Model

Simulated outgoing longwave radiation （OLR） outputs by two versions of the grid-point atmospheric general circulation model （GAMIL） were analyzed to assess the influences of improvements in cloud microphysics and convective parameterization schemes on the simulation of the Madden-Julian oscillation （MJO） and other tropical waves. The wavenumber-frequency spectral analysis was applied to isolate dominant modes of convectively coupled equatorial waves, including the M30, Kelvin, equatorial Rossby （ER）, mixed Rossby-gravity （MRG）, and inertio-gravity （1G） waves. The performances of different versions of the GAMIL model （version 1.0 （GAMIL1.0） and version 2.0 （GAMIL2.0）） were evalu- ated by comparing the power spectrum distributions of these waves among GAMIL 1.0, GAMIL2.0, and observational data. GAMIL1.0 shows a weak MJO signal, with the maximum variability occurring separately at wavenumbers 1 and 4 rather than being concentrated on wavenumbers 1-3, suggesting that GAMILI.0 could not effectively capture the intraseasonal variability. However, GAMIL2.0 is able to effectively reproduce both the symmetric and anti-symmetric waves, and the significant spectra of the MJO, Kelvin, and MRG waves are in agreement with observational data, indicating that the ability of GAMIL2.0 to simulate the MJO and other tropical waves is enhanced by improving the cloud microphysics and convective parameterization schemes and implying that such improvements are crucial to further improving this model＇s performance.

Wavelet analysis of the convectively-coupled equatorial waves

The spatial and temporal distribution characteristics of the main convectively-coupled equatorial waves were analyzed with the OLR data provided by NOAA and the method of wavelet analysis.The results indicate that the wavelet analysis can effectively distinguish MJO,Kelvin,ER,TD,and EMRG wave and the characteristics of their activities in 1992.The propagation speeds of MJO and ER wave are the slowest,following by Kelvin and TD wave and with MRG the fastest.The MJO from the Indian Ocean to the West Pacific Ocean,the Kelvin wave near the International Date Line,the ER and the TD wave around the West Pacific Ocean and the MRG in the eastern of the International Date Line have the biggest wave amplitude.The MJO in boreal winter and spring,the Kelvin wave in boreal spring and summer,the ER wave in boreal autumn,and the TD wave in boreal summer are active.The WMRG wave activates in boreal autumn,whereas EMRG wave appears year-round.These spatial and temporal characteristics agree well with the results of relevant theoretical studies,indicating that the wavelet analysis in the time-frequency domain is another effective method to reveal the evolution of convectively-coupled equatorial waves.