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We examine the dependence of the wind-wind collision and subsequent X-rayemission from the massive WR+O star binary WR~22 on the acceleration of thestellar winds, radiative cooling, and orbital motion. Simulations wereperformed with instantaneously accelerated and radiatively driven stellarwinds. Radiative transfer calculations were performed on the simulation outputto generate synthetic X-ray data, which are used to conduct a detailedcomparison against observations. When instantaneously accelerated stellar windsare adopted in the simulation, a stable wind-wind collision region (WCR) isestablished at all orbital phases. In contrast, when the stellar winds areradiatively driven, and thus the acceleration regions of the winds areaccounted for, the WCR is far more unstable. As the stars approach periastron,the ram pressure of the WR's wind overwhelms the O star's and, following asignificant disruption of the shocks by non-linear thin-shell instabilities(NTSIs), the WCR collapses onto the O star. X-ray calculations reveal that whena stable WCR exists the models over-predict the observed X-ray flux by morethan two orders of magnitude. The collapse of the WCR onto the O starsubstantially reduces the discrepancy in the $2-10\;$keV flux to a factor of$\simeq 6$ at $\phi=0.994$. However, the observed spectrum is not well matchedby the models. We conclude that the agreement between the models andobservations could be improved by increasing the ratio of the mass-loss ratesin favour of the WR star to the extent that a normal wind ram pressure balancedoes not occur at any orbital phase, potentially leading to a sustainedcollapse of the WCR onto the O star. Radiative braking may then play asignificant r\^{o}le for the WCR dynamics and resulting X-ray emission.

Investigating the X-ray emission from the massive WR+O binary WR 22 using 3D hydrodynamical models